Dating Vintage: Using RN Numbers

Ok, we don't plan to write very often about math formulas, but I thought this was pretty useful. While trying to figure out how old a shirt is, I came across this eBay guide on dating clothing via RN, WPL and CA numbers on clothing labels.

The FTC issues registered identification numbers or RNs to businesses residing in the US that are engaged in the manufacture, importing, distribution, or sale of textile, wool, or fur products (note that not all of these types of companies are issued RNs). Starting in 1959, the first number in the series was 13670, and since then there were an average of 2635 RNs per year.

So, while it’s not absolutely precise, you can estimate the earliest date a garment could have been produced with the following formula:

Your RN #
-13670 (first RN # in series)
Total #s between the original and yours/2635 (average #s issued per year) = # of years since issue date
1959 + # of years since issue date = estimated year of issue

For example, I used the formula with the this shirt:


The RN #: 55749
- 13670
= 42079
Divided by 2635
= 16 (The # of years since the issue date)
1959 + 16
= 1975












Therefore, the RN number for LAX, the maker of this shirt, was issued in 1975. This doesn’t mean the shirt was made in 1975, just that the this is the earliest date when it could have been made. Thus, it isn't from the 1960s, for example, though it is possible it is from the 1980s. To figure out a more precise dating on the shirt I would need to use other clues, such as the style, logos, company history, or union tags.