Thanks for the lead, Juvela.
I guess the main differences -- off the top of my head -- between that frame and this one are that the frame I'm asking about definitely has a Cinelli BB shell, stamped "BMZ", and has Columbus SL decals on it (original to the frame).
There are a couple of other differences that you can't see in my close-up photos: my frame has a fluted seattube (for a shorter wheelbase) and a slot along the side of the toptube for the rear brake cable to run in. It's clearly a pretty high-end frame, but what "LM" might mean, I still have no idea.