Here's some information to help you figure out around what year your favorite vintage piece was manufactured.
The Federal Trade Commission's Wool Products Labeling Act of 1939, required that any person, association, or corporation in any form of business manufacturing or selling products containing wool be registered with the United States government.
WPL numbers were issued to registrants starting in 1941 with #00101 and continued until 1959, ending with #13669. The starting zeros were dropped and numbers were only put on clothing labels as 3 or 4 digits until 10,000 was reached in the 1950s, then all 5 digits were used.
After 1959, the formation of the Registration Numbers system was implemented to cover the Wool Products Labeling Act. RN numbers commenced with #13670, following in sequence from the WPL numbers.
WPL or RN numbers cannot specifically date a garment, but are used to determine the absolute oldest a garment can be. In other words, a garment with a WPL or RN number on the label cannot be older than when the number was approximately issued. A formula was created to help determine about what year a garment was manufactured. It is based on the start year and the average amount of numbers issued each year.
For WPL Number Dating:
Divide the WPL number by 759 (average issue amount per year), round up or down and add to 1941 (start year).
For RN Number Dating:
RN number minus 13670 (starting number for RN's), divide by 2189 ( average issue amount per year), round up or down and add to 1959 (start year).
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