The indentation is to give the chainrings clearance so they can turn without rubbing on the chainstay. It is not a Cinelli frame. My gut feeling is that it is a locally built frame. I would give a rough build date of the early 80's. The pump peg was in vogue in the 80's. It looks to have an old Record Campagnolo seatpost probably from the 70's. These were great posts, strong and finely adjustable. If I bought a new frame in the 80's I would still fit one of these seatposts because they were that good.

The Cinelli bars and stem were commonly used in the 80's as well. What is unusual is the black annodised stem. They were more commonly silver annodised. I would have wanted one of those to put on my new bike - if it was my bike.

With Cinelli and Campagnolo components it was probably a pretty good bike built our of a better quality steel tubing. The bottom bracket looks to be Shimano - which seems to be a little out of place. The bottom bracket could have been changed somewhere during the life of the bike. I can't tell what headset is fitted but it looks like it could be Japanese.

By the way, checkout the thread on the bottom bracket (stamped on the shell). With a bit of luck it will be British 1.370 x 24tpi (more common).

It's a pretty good frame. My suggestion - if you want to restore it, choose a groupset you would be happy with (80's vintage). Either Campagnolo, Shimano or Suntour. Clean up the frame (re-paint). Fit the groupset and go for a ride. I don't think you will find the builder but you never know. If it is a local bike, someone may recognise the build features and identify it. The bar and stem are top shelf parts for the 80's. The seatpost is missing parts - replace it.

Best of luck,

Gary.