OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings

1

OSAC 2023-S-0018 Standard 

Test Method for the 

Restoration of Obliterated 

Serial Numbers and Other 

Markings 

Firearms & Toolmarks Subcommittee 

Physics/Pattern Interpretation Scientific Area Committee 

Organization of Scientific Area Committees (OSAC) for Forensic Science 

 
OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings

2

DRAFT OSAC Proposed Standard 

OSAC 2023-S-0018 

Standard Test for the Restoration of 

Obliterated Serial Numbers and Other 

Markings 

Prepared by 

Firearms & Toolmarks Subcommittee 

Organization for Scientific Area Committees (OSAC) for Forensic Science 

Version: 1.0 

September 2023 

Disclaimer 

This OSAC Proposed Standard was written by the Organization of Scientific Area Committees 

(OSAC) for Forensic Science following a process that includes an open comment period. This 

Proposed Standard will be submitted to a standards developing organization and is subject to 

change. 

There may be references in an OSAC Proposed Standard to other publications under development 

by OSAC. The information in the Proposed Standard, and underlying concepts and methodologies, 

may be used by the forensic-science community before the completion of such companion 

publications. 

Any identification of commercial equipment, instruments, or materials in the Proposed Standard 

is not a recommendation or endorsement by the U.S. Government and does not imply that the 

equipment, instruments, or materials are necessarily the best available for the purpose. 

To be placed on the OSAC Registry, certain types of standards first must be reviewed by a 

Scientific and Technical Review (STR). The STR process is vital to OSAC’s mission of generating 

and recognizing scientifically sound standards for producing and interpreting forensic science 

results. The STR shall provide critical and knowledgeable reviews of draft standards or of 

proposed revisions of standards previously published by standards developing organizations 

(SDOs) to ensure that the published methods that practitioners employ are scientifically valid, and 

the resulting claims are trustworthy. 
OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings

3

The STR panel will consist of an independent and diverse panel, including subject matter experts, 

human factors scientists, quality assurance personnel, and legal experts, which will be tasked with 

evaluating the proposed standard based on a comprehensive list of science-based criteria. 

For more information about this important process, please visit our website 

at: https://www.nist.gov/topics/organization-scientific-area-committees-forensicscience/scientific-technical-review-panels 
OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings

4

Keywords: obliteration, serial number, serial number restoration 

This document provides procedures for the restoration of obliterated serial numbers and other 

markings by forensic firearm and toolmark examiners or technicians. 

Foreword

This standard test method document was proposed by the Firearms and Toolmarks Subcommittee 

of the Organization of Scientific Area Committees (OSAC) by submitting a request to the 

American Academy of Forensic Sciences (AAFS) Academy Standards Board (ASB). This 

document is intended to provide procedures for the restoration of obliterated serial numbers and 

other markings by forensic firearm and toolmark examiners or technicians. 

Laboratory policy may inform examiners/technicians as to which steps in the process are 

appropriate. 

 
OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings

5

Table of Contents 

1. Scope Page 6 

2. Normative References Page 6 

3. Terms and Definitions Page 6 

4. Requirements Page 6 

Annex A (normative) Page 13 

Annex B (informative) Page 15
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

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1 1. Scope 

2 

3 This standard provides procedures for the restoration of obliterated serial numbers and other 

4 markings by forensic firearm and toolmark examiners or technicians. These procedures 

5 include the most commonly-used techniques. Other techniques may be available and 

6 appropriate but are beyond the scope of this document. Following these procedures, an 

7 examiner or technician will be able to conduct, document, and report on any results of the 

8 restoration of obliterated serial numbers and other markings. 

9 

10 Only serial number restoration in the context of firearms will be referred to in the remainder 

11 of this document. However, these procedures may be applicable to the restoration of serial 

12 numbers or other markings on firearms and non-firearm items, as well as other markings. 

13 

14 2. Normative References 

15 

16 Best Practice Recommendations for the Safe Handling of Firearms and Ammunition. 

17 

18 Standard Test Method for the Examination and Testing of Firearms. 

19 

20 Klees, Gregory S. "The Restoration of Obliterated Laser-Etched Firearm Identifiers by 

21 Conventional and Alternative Decryption Methods." AFTE Journal 34.3 (2002): 264-267. 

22 

23 Malikowski, Shawn G. "The Restoration of an Obliterated Serial Number and Barcode Using 

24 Digital Photography and Adobe® PhotoShop®." AFTE Journal 36.2 (2004): 237-238. 

25 

26 3. Terms and Definitions 

27 

28 None 

29 

30 4. Requirements 

31 

32 4.1 Background 

33 

34 Many manufactured items have serial numbers for identification. The process of applying 

35 the numbers often deforms the metal or plastic in the immediate area and for a short 

36 distance below the visible number. 

37 

38 Serial numbers can be removed and/or obliterated in a variety of ways. The serial number 

39 may be restored if the removal or obliteration does not extend below the deformed area of 

40 the metal or plastic. Many methods to obliterate serial numbers may, 

41 

42 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

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43 themselves, produce toolmarks identifiable to a suspect tool. If preservation is desired, 

44 these toolmarks must be cast prior to serial number restoration processes. 

45 

46 4.2 Equipment and Materials 

47 

48 Various light sources 

49 

50 Personal protective equipment 

51 

52 Engraver or scribe 

53 

54 Microscope (various types) 

55 

56 Various tools necessary for the disassembly of firearms 

57 

58 Fume/exhaust hood 

59 

60 Chemicals/reagents necessary for restoration (See Appendix A for reagent preparation 

61 instructions) 

62 

63 Magnetic particle suspension (e.g. MagnafluxTM) 

64 

65 Magnets (various types) 

66 

67 Cleaners and/or solvents 

68 

69 Sanding/polishing equipment 

70 

71 Cotton-tipped swabs or other applicators 

72 

73 Power source 

74 

75 4.3 Test Preparations 

76 

77 4.3.1 Use appropriate personal protective equipment. 

78 

79 4.3.1.1 Wear appropriate gloves when using chemical 

80 reagents or when handling evidence contaminated with 

81 chemical and/or biological hazards. 

82 4.3.1.2 Wear eye protection when working with chemical 

83 reagents or operating power tools. 

84 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

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85 4.3.1.3 Work within a fume hood or wear an appropriate 

86 respirator when working with volatile chemical reagents. 

87 

88 4.3.1.4 If an ultraviolet light source is used, minimize 

89 exposure to skin by wearing appropriate protective clothing 

90 and using appropriate eye protection. 

91 

92 4.3.2 Ensure that the firearm is unloaded prior to examination and 

93 follow all appropriate measures for safe handling. Refer to 

94 ANSI/ASB Best Practice Recommendation 068 for the Safe 

95 Handling of Firearms and Ammunition. 

96 

97 4.3.3 Perform function testing and test firing prior to serial number 

98 restoration unless specifics of the case dictate otherwise. Refer to

99 ANSI/ASB Standard 093, Standard Test Method for the 

100 Examination and Testing of Firearms. 

101 

102 4.4 Documentation 

103 

104 4.4.1 Acceptable forms of documentation include, but are not 

105 limited to, worksheets, laboratory notes, sketches, photographs, or 

106 a combination thereof for the general documentation of the entire 

107 restoration process. 

108 

109 4.4.2 Specifically, use photography to document the area of 

110 obliteration before beginning the restoration process and at the 

111 conclusion of the process, to include any characters restored. If 

112 restored characters cannot be photographed, note the reason(s). 

113 

114 4.4.3 Document contemporaneously as restored characters appear, 

115 given they may be transient. 

116 

117 4.4.4 Document the following, as appropriate: 

118 

119 Restoration procedures used 

120 Chemical reagents used and their order of use 

121 

122 Results of reagent check(s) 

123 

124 

125 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

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126 4.5 Evidence Handling 

127 

128 4.5.1 Document the condition of the evidence packaging as received and mark the 

129 packaging in accordance with laboratory protocols. 

130 

131 4.5.2 Mark the evidence for identification in accordance with laboratory protocols. 

132 

133 4.6 Initial Examination 

134 

135 4.6.1 Determine and document the following, as appropriate: 

136 

137 Location of obliterated serial number 

138 Any coatings or trace material present 

139 Suspected method of obliteration 

140 Characters and character remnants visible prior to restoration 

141 Composition of substrate (e.g. ferrous metal, aluminum alloy, etc.) 

142 Possible serial number structure 

143 

144 4.6.2 Determine if the firearm contains a barcode or hidden serial number. The presence 

145 of either may obviate the need for a restoration, depending on laboratory policy. 

146 

147 4.6.3 Determine the restoration technique(s) that will be utilized. Non-destructive 

148 methods such as magnetic particle inspection should be used before destructive methods, 

149 where appropriate, and may be used at subsequent stages of the examination (e.g., before 

150 and after polishing). 

151 

152 4.7 Surface Preparation 

153 

154 It is desirable to remove dirt, debris, paint or other obscuring substances and to smooth 

155 scratches and burrs introduced during obliteration. The surface preparation procedure can 

156 be effective independently, but is more often performed prior to various chemical or 

157 physical restoration procedures. 

158 

159 4.7.1 Use an appropriate cleaner or solvent to remove obscuring material. 

160 

161 4.7.2 Polish the area of the obliteration using a fine grit abrasive. Depending on the 

162 extent of the obliteration, continue polishing until the surface is smooth, removing as 

163 many scratches as possible without destroying the area of deformation. If the obliteration 

164 is deep, it may not be possible or desirable to remove all the scratches. 

165 

166 

167 4.7.3 Document any characters that become visible. If a barcode becomes clear enough 

168 for decryption, then consider the use of one of the methods outlined by Klees or 

169 Malikowski (see references). 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

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170 

171 If all of the characters do not become visible or legible, proceed to the appropriate 

172 restoration procedure. 

173 

174 4.8 Magnetic Particle Inspection Restoration 

175 

176 The magnetic particle inspection technique is used to detect surface or subsurface 

177 irregularities in iron or steel during manufacturing. In conjunction with surface 

178 preparation, use of this procedure can be an effective, non-destructive method to restore 

179 obliterated characters. The magnetic particle inspection technique may be applied at 

180 various stages during the restoration procedure, even after chemical restoration is 

181 attempted. 

182 

183 4.8.1 Determine whether the specimen is suitable for magnetic particle inspection by 

184 ensuring the magnetic field can be adjacent to the area of obliteration. The specimen is 

185 suitable if it is magnetic. 

186 

187 4.8.2 Prepare magnetic particle suspension. 

188 

189 4.8.3 Apply selected magnetic particle suspension to the area of obliteration. 

190 

191 4.8.4 Place a magnet, with the poles on either side of the area of obliteration. This 

192 placement may be adjusted to reveal more or different areas of the obliteration. 

193 

194 4.8.5 If a fluorescent magnetic particle suspension is used, observe the characters under 

195 an ultraviolet light. 

196 

197 4.8.6 Document any characters that become visible during the process. 

198 

199 4.8.7 If no characters become visible, proceed to the appropriate chemical restoration 

200 procedure. 

201 

202 4.9 Chemical Restoration 

203 

204 The chemical restoration procedure, sometimes referred to as the chemical etching 

205 procedure, is suitable for restoration of serial numbers in metal. This procedure, in 

206 conjunction with the surface preparation procedure, is an effective way to restore an 

207 obliterated serial number in metal. 

208 

209 

210 

211 4.9.1 Determine the magnetic properties of the serial number substrate and use 

212 appropriate chemical reagent(s), as listed below in order of increasing reactivity. These 

213 reagents are commonly used in forensic laboratories, however, this is not an exhaustive 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

11 

214 list. Depending on the alloy encountered, examiners may find additional reagents that 

215 perform equally well or better.

216 

217 Magnetic (Ferrous) Substrate: 

218 Davis Reagent 

219 Turner’s Reagent (can also be used as a highlighter) 

220 Fry’s Reagent 

221 

222 Non-magnetic (Non-Ferrous) Substrate - Zinc 

223 Ferric Chloride 

224 Phosphoric Acid/Nitric Acid (Knowles Reagent) 

225 25% Nitric Acid (used as a highlighter) 

226 

227 Non-magnetic (Non-Ferrous) Substrate - Aluminum 

228 Ferric Chloride 

229 Acidic Ferric Chloride 

230 10% Sodium Hydroxide 

231 25% Nitric Acid (used as a highlighter)

232 

233 Test the chosen reagent in an area away from the serial number location in order to 

234 determine if the reagent is reacting appropriately for the substrate. Document the 

235 result(s) of this test. Do not proceed with a reagent that does not react appropriately. 

236 Any additional reagents used later in the process should also be tested for reactivity. 

237 

238 4.9.2 Apply the reagent to the area of obliteration utilizing cotton tipped applicators or 

239 swabs that have been moistened with the chemical solution. Alternating between 

240 (particularly the reagents for zinc alloys) or changing reagents may assist in the recovery 

241 process. 

242 

243 4.9.3 Document any characters that become visible. 

244 

245 4.9.4 At the conclusion of the chemical restoration process, rinse the area that was in 

246 contact with the reagent with water and apply a preservative such as oil, a clear lacquer, 

247 etc. to inhibit corrosion. 

248 

249 4.10Electrochemical Restoration 

250 

251 The electrochemical technique using the standard chemical etchants is an enhanced form 

252 of chemical restoration, in which the application of a voltage potential assists with the 

253 oxidation of the specimen. This procedure, in conjunction with the surface 

254 

255 preparation procedure, may be an effective way to restore an obliterated serial number in 

256 ferrous metal. 

257 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

12 

258 4.10.1Attach the specimen to the positive terminal of the power supply via an alligator 

259 clip. Turn on the power supply and adjust the voltage. Three to six volts is typically 

260 sufficient. 

261 

262 4.10.2Thoroughly soak the cotton tip of an applicator with the appropriate chemical 

263 etchant and attach the negative terminal of the power supply to a moistened area at the 

264 base of the cotton tip. 

265 

266 4.10.3Wipe the area of obliteration with the moistened tip of the cotton swab. 

267 

268 4.10.4Document any characters as they become visible. 

269 

270 4.10.5At the conclusion of the electrochemical restoration process, rinse the area that was 

271 in contact with the reagent with water and apply a preservative such as oil, a clear lacquer, 

272 etc. to inhibit corrosion. 

273 

274 4.11Heat Restoration in Plastic Surfaces 

275 

276 The application of heat can be a suitable restoration method for serial numbers in plastic. 

277 The die stamping or embossing process is a form of cold-working plastic. A side effect 

278 of cold-working is the decrease of that item’s ability to resist heat. 

279 

280 4.11.1Carefully apply heat to the area of obliteration using a high intensity lamp, heat 

281 gun, or other suitable heat source, using caution so as not to melt the surrounding area. 

282 

283 4.11.2Continue the application of heat until the plastic in the obliterated area starts to 

284 soften. 

285 

286 4.11.3Document any characters as they become visible. 

287 

288 4.12Test Reports 

289 

290 4.12.1The test report shall include a description of any firearm or other item that is 

291 examined. At a minimum, the description of a firearm shall include, if known, the 

292 make/manufacturer, firearm type, model, caliber/gauge, and any legible serial number 

293 characters. 

294 

295 4.12.2The entire structure of the serial number, if known, should be represented in the 

296 report, to include fully and partially restored characters, and locations of characters that 

297 could not be restored.

298 

299 

300 

301 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

13 

302 Annex A 

303 (normative) 

304 

305 Reagent Formulas 

306 

307 

308 A.1 Reagent Formulas 

309 

310 A.1.1 10% Sodium Hydroxide 

311 10 g Sodium hydroxide 

312 90 mL distilled water 

313 

314 A.1.2 25% Nitric Acid 

315 25 mL nitric acid 

316 75 mL distilled water 

317 

318 A.1.3 Acidic Ferric Chloride 

319 25 g ferric chloride 

320 25 mL hydrochloric acid 

321 100 mL distilled water 

322 

323 A.1.4 Davis’ Reagent 

324 5 g cupric chloride 

325 50 mL hydrochloric acid 

326 50 mL distilled water 

327 

328 A.1.5 Ferric Chloride 

329 25 g ferric chloride 

330 100 mL distilled water 

331 

332 A.1.6 Fry’s Reagent 

333 90 g cupric chloride 

334 120 mL hydrochloric acid 

335 100 mL distilled water 

336 

337 A.1.7 Phosphoric Acid/Nitric Acid (Knowles Reagent) 

338 98 mL 85% phosphoric acid 

339 2 mL concentrated Nitric acid 

340 or 

341 50 mL concentrated phosphoric acid 

342 3 mL concentrated nitric acid 

343 

344 

345 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

14 

346 A.1.8 Turner’s Reagent 

347 2.5 g cupric chloride 

348 40 mL hydrochloric acid 

349 25 mL ethyl alcohol 

350 30 mL distilled water 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

15 

351 Annex B 

352 (informative) 

353 

354 Bibliography 

355 

356 Deats, Marcellus. "Serial Number Restoration Information." AFTE Journal 12.3 (1980): 82-83. 

357 

358 Desrochers, C., et al. "Serial Number Restoration in Plastic Using a Heat Gun." AFTE Journal 

359 32.4 (2000): 367. 

360 

361 James, Stuart H. and Jon J. Nordby, eds. Forensic Science: An Introduction to Scientific and 

362 Investigative Techniques. 2nd ed. Boca Raton: CRC Press, 2005. 

363 

364 Klees, Gregory S. "The Restoration of Obliterated Laser-Etched Firearm Identifiers by 

365 Conventional and Alternative Decryption Methods." AFTE Journal 34.3 (2002): 264-267. 

366 

367 Malikowski, Shawn G. "The Restoration of an Obliterated Serial Number and Barcode Using 

368 Digital Photography and Adobe® PhotoShop®." AFTE Journal 36.2 (2004): 237-238. 

369 

370 Mathews, J. Howard. Firearms Identification. Vol. 1. Madison, Wis.: Univ. of Wisconsin Press, 

371 1962. 

372 

373 Miller, Ken E. "Current Assist for Die Stamp Impression Restoration." AFTE Journal 4.3 (1972): 

374 38. 

375 

376 O’Reilly, W.E. "Magnetic Restoration of Serial Number." AFTE Journal 2.NL07 (1970): 26-27. 

377 

378 Roberts, Van. “Restoration of Serial Numbers in Plastic.” AFTE Journal 13.4 (1981): 40-47. 

379 

380 Schaefer, Jeffrey. "Serial Number Restoration Observations." AFTE Journal 19.3 (1987): 276-

381 278. 

382 

383 Serial Number Restoration Reagents for Plastics. Sirchie Finger Print Laboratories, n.d. Web. 18 

384 Nov. 2014. 

385 

386 Polk, Donald E. and Bill C. Giessen. “Metallurgical Aspects of Serial Number Recovery.” AFTE 

387 Journal 7.2 (1975): 38-52. Rpt. in AFTE Journal 21.2 (1989): 174-181. 

388 

389 Treptow, Richard. National Aeronautics and Space Administration. Handbook of Methods for 

390 the Restoration of Obliterated Serial Numbers. Chicago: Chicago State University, 1978. 

391 

392 Turley, Dennis M. "Restoration of Stamp Marks on Steel Components by Etching and Magnetic 

393 Techniques." Journal of Forensic Sciences 32.3 (1987): 640-649. 

394 
 OSAC 2023-S-0018 Standard Test Method for 

the Restoration of Obliterated Serial Numbers 

and Other Markings 

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395 United States. Bureau of Alcohol, Tobacco, Firearms, and Explosives Laboratory. Serial Number 

396 Restoration Handbook. 1999.

397