Originally Posted by Hondo44

Have you checked the front sight with good light and magnification. It's clearly not a factory sight, but even if not a King sight they're usually stamped with the maker's name. There were several available back in the day, and S&W would even install an after market sight of your choice.

If the rear sight is a factory installed target sight, you have a pretty scarce TL and more desirable than a King sight converted standard model.

It there's a matching serial # to your gun on the bottom side of the rear sight tang, you have a factory target model TL.