Companies that sell merchandise made of textile, wool or fur (e.g., clothers) in the U.S. are generally required to put a label on the garment giving the name of the material, the company and the country where the garment was made (under 15 U.S.C. § 70, 15 U.S.C. § 68 and 15 U.S.C. § 69). However, U.S. companies can get a Registered Identification Number from the Federal Trade Commission and put that on the label instead.
You can look up RN Numbers in the FTC's RN Database at www.ftc.gov/bcp/rn/rn.htm. The FTC Form 31 that a manufacturer files to apply for an RN Number is also posted at at that address.
There is a Canadian equivalent to RN Numbers called CA Identification Numbers or just "CA Numbers." The Canadian Competition Bureau posts information about CA Numbers and a CA Search at www.competitionbureau.gc.ca/eic/site/cb-bc.nsf/eng/h_02575.html.