This one (as you can see from your copy of the SCSW) 'should' have shipped in 1947, but they were slow sellers. A factory letter will tell you this and if the stocks are original to the gun; these usually came with the smaller Magna stocks. As Big Larry implied, the narrow rib/tapered barrel were earlier production, and the wide rib/untapered version was called the Heavy Masterpiece; this version was made so the K-22, -32 and -38 equaled out in weight and balance.
You are on quite a roll with S & Ws recently
. Enjoy!