i just found this half rotten bike in the backyard now trying to find out its story. A little help to identify brand, model and age would be much appreciated.

Here are some facts:

- the only sticker on the frame says: reynolds 531
- the bottom bracket has two cutouts and carries a two digit number (57)
- the fork has an "S" on both sides of the crown (Mauro Sannino?!)
- Cinelli stem with 3t bar "mod competizione"
- most parts are shimano600 so i think its from the early 80s

pics attached (please let me know if you need to see more details)

Thanks