So, someone got this—anyone here? Nice deal for a seldom-seen board, in any case.
I checked with the seller. This keyboard has two-piece keycaps.
That's good to know. The only one I'd ever seen was one-piece, but considering this one and the one Brandon describes at ClickyKeyboards are both two-piece, I've changed the WP entry's comment to read:
Uncommon 1391401 variant. Also known to have one-piece keycaps.
Regarding pricing, there's 4 BIN M's on ebay right now in similar condition with lower prices including shipping, and one for $35 shipped that needs the cable replaced.
Well, most of us agree that part of the fun is the slight differences between the nearly Model M 100 variants ("part numbers") IBM produced. Sometimes the differences are obvious—special legends, a real speaker, different controller, etc.—and sometimes only the p/n itself is different, leaving us to wonder why it had a special designation.