Here you go:
Smith & Wesson Historical Foundation - Letter Process - Insuring that the rich history of Smith & Wesson will continue for generations to come
Don may just have something to do with the lettering thing
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The tricky part about ship dates is popular models are sold quickly after production, unpopular ones not, and S & W never ships in numerical order. The .38 Centennial was not a strong seller and it may have sat on a shelf for months, or years, after it was made.