I've got one of these frames, with the same periwinkle/royal blue splatter paint job. My impression is these frames are from the first run of Superforms described in the article. I got it used, set up with 26" (ISO 559) wheels. Ritchey Tom Slick tires, 26"x25mm, just barely cleared the frame. You may have to use 20mm tires on 650c rims.

I found the bike incredibly quick. It felt like it 'planed'. I hated the skinny tires though. I tried a few different seat and cockpit setups and eventually took it apart, with the idea of someday crimping the chainstays and trying to fit a 26x1-1/8" tire... That was four years ago.