Wow, that was fast. Pistol arrived today after being picked up by UPS exactly 7 days ago. Shooters cap and a new mag with the extension was included. Hammer was replaced, it definitely has a new hold open.
The letter enclosed states the pistol was upgraded with all the running improvements made as the LCP line progressed. "It is likely the only one you will be able to see is the new manual slide hold-open, but other, more subtle improvements have been incorporated too, and these should make your LCP even more rugged and reliable in the best Ruger tradition."
Dry firing a few times, it definitely seems smoother. I'll take it down and see if anything else jump out as replaced, new, or worked over.