We're still learning. As to exact numbers, we'll never know. I've got 3 of them, and an extra hammer. BruceHMX sold one recently in the classifieds. I've seen and heard about a few more. While there are guns with the hammer down in the 667,000s range, I don't know if they letter like that or if the hammer was an aftermarket addition. My 3 have serials in the 673-4,000s. I do know that K22s in the 670s are much more frequently seen with standard hammers. I've not seen one above 680,000 with a HBH. Also remember that the serial number sequence was shared with M&Ps.
If someone suggested that 500 were made, I wouldn't argue much. I seriously doubt that 1,000 were made. It also wouldn't suprise me to learn only 250-300 were produced. And I'm only shooting from the hip based on the K22s I've seen.
I do know that spare HBH were produced and never installed on guns. Hugh May used to tell a story about him finding and buying 3 variations in a single box. That included 2 Ns and a K frame mounted style hammer. He didn't include the K as used on M&P targets. Those are even harder to locate.
I believe that Dave/Merlindb picked up the K32 that was offered up a while back. There was no confirmation that it shipped with its HBH, but no way of proving it either way. If my memory is correct the seller went to great lengths to get Roy to letter it like that and he refused.
I put in that last to get anyone wandering shows to keep an eye open for M&P or M&P targets that might have the feature. Its worth picking one up if cheap enough.
Recent sales seem to support the idea that any prewar gun in collector condition with a HBH is worth $1000 or more.
As for front sights, anything goes. S&W in that time period would install anything a customer wanted. Just as frequently, customers had the front sights changed to ones they liked better or wanted to try. Don't reject an otherwise good deal because you think the front sight doesn't comply with SCSW. They'll be the first to tell you that variations do exist. The proper way to read Jims book is as a general guide, not as a bible without exceptions. It wasn't intended to be used that way.
And in all this, don't ever forget to inspect the gun for signs of alterations like signs of pins having been pushed out, etc. Wear and tear on the parts should seem equal.
