Originally Posted by Otis

I'd imagine Schwinn bought a lot of these at a time and used them well past the change in design. The only Italian bikes I've owned with "open C" drops have been from the 50's. I currently have four Italian frames built between '60-'64 and they all have closed "C" drops.

I've read that the "open C" was replaced in 1959 (at least as far as the shifters and skewers go). But again, I think you need to allow at least a few years leeway in trying to date a complete bike from parts like that. Who knows what sat on shelves for how long, etc.

I'm not sure if the OP has confirmed the oil-ports on the BB shell, but I would say this is a early to mid 60's Cinelli.