Oh man that's nice. Are you sure that's a 54.5 seat tube? Looks like a lot of parts were switched out, but nice nonetheless.
Measured it again. I get somewhere between 54.5 and 55cm. The PO received it as a frameset and built it up from there with spare parts. As a result there are some oddball things going on (bladed spokes, painted white Nitto stem), but for the most part the component replacements are practically minded (sealed cartridge BB, freehub, dual-pivot brakes). I'm not complaining, although for aesthetic reasons I'm changing a few things around.
It wasn't very common for most, but it was quite common for lotus. I've seen a legend with campagnolo and many (most) higher end lotus bikes were using Columbus tubing. My odyssey was SL.
So you mean, Campy dropouts with Columbus tubing? That's more of what I'd expect. But I get the feeling Lotus had more of a practical mix-and-match to get the job done kind of philosophy (a la Bridgestone circa Grant Peterson).