The numbers on the Yoke & frame are assembly/work numbers, used to ke6p parts together before the serial numbers were stamped. the assembly/work numbers will also be on the grip frame and on the back side of the sideplate and should match if all the parts are original. I have several ads in my files from Parker-Hale & other Brit gun makers offering .22LR conversions of the Pre-Victory Model S&Ws bought by the Brits before WW2. Various techniques were used from lining cylinders & barrels to new barrels & cylinders. Sounds like your gun was one of the liners jobs. Your gun was most likely caliber .38S&W before the conversion. Ed.