Tiny 1986 Cannondale SC400
 

CL $30, advertised as a "city bike", 37cm cc, 39cm ct, crazy looking ht-tt-dt cluster has some major filets, I bought it just because.....$30 why not. Rear spacing is 130mm. Steel fork. I'll strip it and decide what to do with it.

Brian

Wow that is odd but cool. More pics! :-)

Cool. 🙂 I imagine the welders had to stop & scratch their heads a bit, if they welded several different sizes of frames. 🤔😁
As far as dating it, I'd think late '80s or early '90s, with that non-lugged steel fork.

According to vintagecannondale.com, the logo on this frame's head tube was in use from '83 through '89. To narrow it down to a specific year, the OP can cross-reference his the serial number to the info on that site :
Vintage Cannondale ? Serial Numbers & Information | VintageCannondale.com

Depending on the year made, the serial number may also give some other information like production date, frame size, and dropout spacing. (Although you've already got most of that stuff figured out.)

Show the rest of that interesting cannondale please.