Regarding dating the pistol , Smith & Wesson apparently decided in mid-1957 to start putting model numbers on their revolvers. I've read one review where this occurred in September 1957. On another website regarding serial numbers my pistol would be dated to 1958 and that's what Smith And Wesson told me when I called them directly with the serial number. that's probably incorrect or somethings inconsistent since there's no model number on my revolver and if Smith started putting model numbers in September 1957 then that was overlooked with this revolver, or the serial number and build and ship dates are different/in accurate. This is a known problem as I understand it. There have been guns reported with earlier serial numbers, but not shipped until a year or two later which confuses the date of production with the date of shipment.
I highlighted the key word in your first sentence. Management decisions are seldom (if ever) implemented immediately. There are lots of reasons for that. But it is a fact that we have never found a single model marked gun (of any model) that left the factory with a model number before 1958.
I've seen the September date as well. It allegedly applied to the Model 10 .38 M&P. I have no way of knowing whether any Model 10 revolvers were actually model marked in September, 1957, but it seems to me that the story is probably apocryphal. In any case, model marked guns certainly did not ship until various times in 1958.
Regardless, since we are not talking about fixed sight K frames in this thread anyway, you should look at the information I posted previously. For your convenience, I'll repost it here.
On the K frame target models, the first known appearance of a model number by serial number goes like this:
K-38 Masterpiece Model 14 (a special order unit) - K314496
.357 Combat Magnum Model 19 - K316819
K-22 Masterpiece Model 17 - K326533
All of those shipped in 1958.
Your K-22 is 2300 numbers lower than the lowest known serial number on a Model 17. I don't think you should assume that the model number was simply "
overlooked" on your revolver. It is much more likely that when yours came down the line, they had not yet started model marking the K-22 Masterpiece.
To restate the obvious, even if they did mark some Model 10s in September, 1957, that certainly does not mean they were model marking all models that early. It is a near certaintly that they were not.