SPC, since your K22 Masterpiece falls into that time frame, it has some specific features. These revolvers are sometimes referred to as “narrow rib” guns because they came before the heavier barrels (early ‘50s on) that had a wider rib to complement their heavier barrels. The pride of workmanship and inherent quality of S&Ws in that time frame was at a peak, and every Masterpiece of that period that I’ve encountered (regardless of caliber) has been very well fitted and a fine shooter. My 1948 K22 came to me via an auction, and it didn’t come up until everyone was pretty well “spent out” so I picked it up at a bargain price… that said I don’t see it ever being for sale!
You inherited a very fine revolver from you FIL. As mentioned above, the fit and finish of the early K-22s make them some of the finest .22 LR revolvers ever produced. Mine is also a 1948 (K40403) that was probably shipped around the same time as yours, and has the 4-line S&W address on the right side of the frame. I believe that a previous owner did a little trigger job on mine because it has a hair trigger in single action. We always appreciate photos, so if you could post a couple of your K-22 it would be greatly appreciated. Enjoy!