I should note that this was perfectly legal at the time, in a way that it would absolutely, totally not be now. Firearms manufacturers in the United States before 1968 were not required by law to give their products serial numbers at all, and those which chose to (and to be fair, most did) were under no obligation to make them unique. In Stevens's case, they only seem to have numbered their products for internal reference, and since far fewer than 25,974 rifles were ever going to be on the company's own books at any one time, the system was considered adequate. If one of these rifles were to be exported to a foreign country and then reimported to the United States, it would have to be issued a new, unique serial number by its importer, but as pre-'68 domestic production, they're grandfathered.
It's impossible to accuratly date a Visible Loader - your 'serial number' is really more of a rotating assembly number consisting of a letter & a number ranging from 1 to 999, starting over again after Z999 - you will never find a Visible Loader with a four digit number (some have been reported but it always has turned out that the letter was missread as a number, like a B thought to be an 8). My best guess is that all of these numbers reapeated at least 4 or more times over the years of production and it seems that all letters of the alphabet may have been used, even those that are hard to tell from others like O & Q.
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