Its closest to a Nuova Strada, but I am not absolute on that.
There was a "reject" batch of frames and forks that were built on contract but not accepted to be labeled as a Masi.
This one does not really fit that look either.
The Nuova Strada was to have SLX for most of its run, you might look for that inside the bottom bracket.
Only other dart toss would to be to contact Jim Allen who painted many for much of the 80's.
Especially during the Italy contract era, he may remember. Remember its has been 30 years.