Back from elk hunting with one in the back of the truck. This used to be alot easier. These things are heavy; birds are much easier to lug around. FWIW, I answered my own question after I asked it by reading George Madis's book on the Model 12 a few nights ago. He seems to agree with Riffle by saying 1934 (he is unclear as to when in the year that occurs, so maybe December?). He says 1947 for the flattened forend.