Bought this on CL a couple months ago. Seller claimed it was a Cinelli Super Corsa. Others have said it isn't but I'm not up on Italian bikes well enough to know. Campy 26.4mm seatpost (stuck for now, unfortunately), Campy HS, unbranded Italian BB. Campy dropouts, filed lugs. Came with usual NR drivetrain, Cinelli bars, some obviously non-original Suntour stuff. Full chrome, no sign of any decals, no serial number or any sign of one. Any help greatly appreciated.

https://imgur.com/a/jUiCV

Not a Cinelli as far as I can tell.
Flat crown
Wrap-around seat stays
Eyelets on dropouts
odd (but pretty) dropout/stay junction.
No rivet holes for head badge.

Not a Speciale Corsa (or Super Corsa, if you prefer) and probabaly not a Cinelli of any kind. The flat fork crown means it's not an SC, although the Cinelli Model B had flat fork crowns. But what makes me say "not any kind of Cinelli" is the seat cluster. I have never seen that kind of set stay attachment on any Cinelli, in person or in a photo - the style looks more British to my eye than Italian. Also, the seat post bolt is not the kind Cinelli used. Finally, classic SC's used a 26.2mm seat post, not 26.4.

The front drop out attachment style looks wrong to me also, but I am less certain about that.

So I am all but certain it is not a Cinelli of any persuasion, and quite certain it is not an SC, but it does look like it could be pretty nice frame in its own right, assuming you can get the stuck seat post out without damaging the frame. (There are other threads here on how to do that.)

For educational purposes, you can get a lot of visual information about what classic Cinellis look like on Classic Rendezvous and on Cinelli Only. Sorry for the lack of links, but they come right up if you google them.

Screams French to me, with the wrap-over stay caps and fish-mouth stay/fork ends. The metal work is rather crude, and what is with the lack of definition around the lug/shell shorelines? It's not like chrome builds up at the joints the way a too-thick paint job does, so that's a little strange.

It's surely not a Cinelli.

DD

I agree with DD that it looks French. Looks like an interesting treatment of the lugs, sort of rounded edges with some fine feathering at the edges, but it's hard to tell with the reflection in the photos. If you remove the locking nut on the headset you should see an inscription telling us the thread diameter and pitch. This may help us to narrow down the nationality. I can't see what bottom bracket is on it but diameter and thread pitch of BB will also help. Not that some BB fixed cups have reverse threading.
Brent

agree with all the thoughts and will add the fork blade x-section looks much more "Reynolds" than "Columbus" but I'd say the 26.4 seatpost is a strong clue for Reynolds in a metric (likely French or possibly Swiss, Belgian, Spanish?) flavor...measure the ODs of the main tubes and confirm the HS threading...if it's really an Italian BB shell then we have a weird combo, here.

Looks like a Pretty nice Frameset to me. Whatever it is.

French bike should have a 68mm wide bottom bracket shell. Italian shell would measure 70mm wide.

In some respects, it looks like the lugs were additionally filed down, almost flattened, before chroming so I wonder if the chrome was a rechrome job, not original. It would be instructive to see the bottom bracket from below to see if any numbers or markings were stamped in or if they were filled with chrome also. The original seller sure was misrepresenting this as a Cinelli. Most Cinelli lugs will have a few decreasing diameter holes in the tops and inside the fork heads where they meet the crown.

Imaginative seller! It's not a Cinelli.

Sorry to be the bearer of bad news.

Most other suggestion are going in the right direction.

26.4mm was the standard size seatpost for metric diameter tubes with a 1.0mm x 0.7mm wall thickness used for most production French frames back then. Reynolds 531 or maybe Metric Columbus SP.

Fish mouthed rear stay and forks ends are definitely French.

Could be a Stella frame or a top end Motobecane from the late 60's to early70's. Or it could have been produced by some small French constructeur (local frame builder). .

The workmanship looks good in places but someone got carried away with a file on the lugs. Were they trying to thin the lugs or did a ham fisted amateur attempt a frame repair???

I'd have someone who knows what to look for as regards to damage or repairs check out the frame before I put any work into it.

Chas.