What follows is an opinion from a United States Court of Appeals.
Intervenors who participated as parties at the courts of appeals should be counted as either appellants or respondents when it can be determined whose position they supported. For example, if there were two plaintiffs who lost in district court, appealed, and were joined by four intervenors who also asked the court of appeals to reverse the district court, the number of appellants should be coded as six.
When coding the detailed nature of participants, use your personal knowledge about the participants, if you are completely confident of the accuracy of your knowledge, even if the specific information is not in the opinion. For example, if "IBM" is listed as the appellant it could be classified as "clearly national or international in scope" even if the opinion did not indicate the scope of the business. 

Your task concerns the first listed appellant. The nature of this litigant falls into the category "private organization or association", specifically "business, trade, professional, or union (BTPU)". Your task is to determine what subcategory of private association best describes this litigant.

Opinion:
AMALGAMATED CLOTHING WORKERS OF AMERICA, AFL-CIO, Petitioner, v. NATIONAL LABOR RELATIONS BOARD, Respondent, Henry I. Siegel Co., Inc., Intervenor. NATIONAL LABOR RELATIONS BOARD, Petitioner, v. HENRY I. SIEGEL CO., Inc., Respondent. HENRY I. SIEGEL CO., Inc., Petitioner, v. NATIONAL LABOR RELATIONS BOARD, Respondent, Amalgamated Clothing Workers of America, AFL-CIO, Intervenor.
Nos. 21086, 21131, 21316.
United States Court of Appeals District of Columbia Circuit.
Argued March 20, 1968.
Decided July 15, 1969.
Certiorari Denied Jan. 12, 1970.
See 90 S.Ct. 556.
Mr. Clifford D. Reznicek, New York City, of the bar of the Supreme Court of New York, pro hac vice, by special leave of court, with whom Mr. Jacob Sheink-man, New York City, was on the brief, for petitioner in No. 21,086 and inter-venor in No. 21,316.
Mr. Elliott Moore, Attorney, National Labor Relations Board, with whom Mr. Arnold Ordman, General Counsel, Mr. Dominick L. Manoli, Associate General Counsel, Mr. Marcel Mallet-Prevost, Assistant General Counsel, and Mr. Harold B. Zanoff, Attorney, National Labor Relations Board, were on the brief, for respondent in Nos. 21,086 and 21,316 and petitioner in No. 21,131.
Mr. Osmond K. Fraenkel, New York City, for intervenor in No. 21,086, respondent in No. 21,131, and petitioner in No. 21,316.
Before BAZELON, Chief Judge, PRETTYMAN, Senior Circuit Judge, and WRIGHT, MeGOWAN, TAMM, LEVENTHAL, ROBINSON, MacKIN-NON, and ROBB, Circuit Judges.
PRETTYMAN, Senior Circuit Judge:
In this case the Labor Board set aside an election on account of unfair labor practices by an- employer and thereupon issued a bargaining order upon the evidence of authorization cards. Upon the authority of the opinion and decision of the Supreme Court in NLRB v. Gissel Packing Co., Inc., et al., the decision and ruling of the Board are affirmed. It will present an appropriate order of enforcement.
. 395 U.S. 575, 89 S.Ct. 1918, 23 L.Ed.2d 547 (1969).

Question: This question concerns the first listed appellant. The nature of this litigant falls into the category "private organization or association", specifically "business, trade, professional, or union (BTPU)". What subcategory of private association best describes this litigant?

Choices:
Business or trade association
utilities co-ops
Professional association - other than law or medicine
Legal professional association
Medical professional association
AFL-CIO union (private)
Other private union
Private Union - unable to determine whether in AFL-CIO
Public employee union- in AFL-CIO (include groups called professional organizations if their role includes bargaining over wages and work conditions)
Public Employee Union - not in AFL-CIO
Public Employee Union - unable to determine if in AFL-CIO
Union pension fund; other union funds (e.g., vacation funds)
Other
Unclear

Answer: 5