I just duplicated your post - didn't see it until after I made the post. Made the post after seeing this creature in Ebay. Tried to delete my post but I can't. Hopefully a moderator will remove it. Apologies.
I can kick in a bit of info about half-frame, though, because I've been using it all my life. By the time the FM2 was out, the Pen FT was long gone. It was victim of it's own success - because of the film industry's class action suit against Olympus (Kodak, Ansco, Agfa and Fuji said that it would substantially harm their film business), Olympus settled out of court, and introduced the OM1.
The half frame was pretty much dead by this time, 1974 I believe.
The Olympus never had a really bright finder, and the Police force that ordered it (Norwegian) wanted 100. (The finder of the FM2 is very bright, which would be much better for surveillance work.) Only about 40 were made - Nikon withdrew the offer because it cost them more to make it than the deal was worth. It essentially had to be hand built.
So this piece is a curiousity, and for collecters like me, Nirvana. If I had 4 grand, I'd buy it. The only other quality SLR half frame was the original Konica Autoreflex, which had a switch allowing the user to go from full to half easily, on the same roll. 1 hour places hate it!
The Konica is a very nice camera, and I'm lucky enough to have two. Still have one as a user!