Very nice revolver. Is the replacement sight package stamped Micro, by any chance? The rear component has the same profile as the sights on a modified .455/Second that I picked up on a whim about 15 years ago. The front sight is a kind of graceless slab, but it could be cut to resemble the one on Jeff's 1917. Converting the .455 to.45 Colt involved planing the recoil shield. The caliber marking ".455 SW" is placed above and to the right of the original S&W 45 DA rollmark. The rear sight is stamped Micro.
After WWII the King Gunsight Company was stumbling, and some its staff left to found Micro (April 1947, according to a post in the archives). The date on the conversion invoice in the top post is, I believe, August 19, 1949, so Micro sights would have been available from the new startup. I don't know the date of the conversion on my gun, but now that I know S&W would do these conversions, I need to ask the SWHF for a document search.