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                                                                   EXHIBIT 10.51


                            SUBLEASE AMENDMENT NO. 1

This Amendment No. 1 is to Sublease dated May 1, 1995, between Arthur A. Riedel,
dba The Celtic Investment Co., as Lessor, and World Security Services Corp., as
Lessee. Lessor and Lessee are jointly referred herein as "the parties".

Whereas Lessee desires to Sublease an additional area, connected to the existing
Sublease Premises;

         NOW, THEREFORE, the parties agree, good and sufficient consideration
having been given and received:

         1.   This Sublease Amendment is effective as of April 15, 1998
              ("Effective Date"), or as may be adjusted to Occupancy Date.

         2.   Paragraph 1 of the Sublease, is amended by the addition of the
              following as of the Effective Date:

                    Revised EXHIBIT A, attached hereto, shows the original
                    Subleased premises, plus area added by Amendment No. 1
                    outlined in red. The additional premises contains
                    approximately 300 square feet, and the total Subleased
                    Premises, with this Amendment collectively contains
                    approximately 3,300 square feet, plus an adjoining storage
                    area containing approximately 150 square fee.

         3.   Paragraph 3 of the Sublease, Rental, is amended by the
              substitutions of the following as of the Effective Date:

                    Rental: During the remaining Term of this Sublease, Lessee
                    shall pay Lessor Three Thousand Three Hundred and No/100
                    Dollars ($3,300.00) per month beginning with the Effective
                    Date, exclusive of the provisions in Paragraph 8, and with
                    the same sum due on the first day of each month thereafter.
                    If the Effective Date/Occupancy Date is other than the first
                    of the month, the rental for that month will be prorated.

              The monthly rentals due shall be paid at Lessor's offices, 4511 N.
              Channel Avenue, Portland, Oregon 97217 (or such other address as
              Lessor may designate in writing).

         4.   Paragraph 8 of the Sublease is deleted in its entirety and the
              following is substituted in its place:

              8. Increase in Annual Operating Costs:

                 A. In lieu of annual increases in rent or pass-throughs of
                 annual operating costs to Lessee, resulting from increases in
                 annual operating costs, excepting any increase in the minimum
                 monthly ground rent or off-site common area maintenance charges
                 as established by and paid to the Port of Portland under the
                 terms of the Master Lease, Lessor has established a five
                 percent (5%) annual increase, payable monthly, over the then
                 current base rental.

                 B. In the event that the Port of Portland (refer Paragraph 22)
                 increases the minimum monthly ground rent or off-site common
                 area maintenance charges over that of the preceding year,
                 Lessor shall furnish to Lessee a statement showing the minimum
                 monthly ground rent and the off-site common area maintenance
                 charges paid to the Port of Portland for the immediately
                 preceding year, together with the new minimum monthly ground
                 rent and/or off-site common area maintenance charges to be paid
                 to the Port of Portland, and the increase over that of the
                 immediately preceding year. Lessee's pro rata share of such
                 increase will be shown on the statement and future monthly
                 statements. The pro rata share will be based on the percentage
                 of the rentable square footage of the Subleased premises (.04%)
                 to the total Ports O'Call Demised Premises rentable square
                 footage, multiplied by the amount of the increase as shown on
                 the statement, not to exceed $25.00 per month over the base
                 year 1998.

All other terms, conditions and provisions of the Sublease, as amended, not
expressly amended herein, shall remain in full force and effect.

Dated this 11th day of March, 1998.

WORLD SECURITY SERVICES CORP.

By: /s/ HANK SLOVDA
   ------------------------------------
Title:        President
"LESSEE"


A.A. RIEDEL, dba THE CELTIC INVESTMENT CO.

By:
   ------------------------------------
Title:        Agent
"LESSOR"