I'll start by saying MIM doesn't necessarily bother me. I'm just curious. Do we know which OEM parts of the p-series pistols, if any, are MIM? Any knowledge of whether this has changed over the years?

Need visual inspection. The two most obvious parts externally that you can tell right away if they are MIM are the hammer and the trigger. A line running right down the middle of the hammer indicates MIM. Hollowed back trigger, except the original P225 one, indicates MIM. The short reach trigger is MIM.

From what I've seen on my newest SIG (an M11-A1 with a 2023 build date), the trigger, locking insert, takedown lever, hammer, and sear are all MIM. However, they don't have the faint mold line running down the middle anymore. Instead they have a little circular mark (likely where the part was broken off of its stem in the mold frame), which often isn't visible until the part is removed from the gun. Older MIM parts will have the line running down the middle though.

Most (all?) current P-22x SIGs have a MIM take-down lever. With a faux rivet head for that olde tyme look.

And the MIM part is better than the original two-piece steel take-down lever. The pieces sometimes loosened, letting the thumb tab drag on the frame, scratching it.

I've seen some 3D printed 1911 parts at a "tech day" for a company that, among many other things, supplies 3D printing powders and resins. I'm going to venture a guess that 3D printing of small gun parts will replace MIM eventually.