Looking at the decals:

The head tube decal -according to B.Hovey's site (http://bhovey.com/Masi/MasiBits/Head.htm)- indicates that the bike was built between 78-83.

While there is no exact match on the side tube decal -according to B. Hovey's site (http://bhovey.com/Masi/MasiBits/STPic.htm)- it looks very much like the side decals from '84-'90.

Again, cyclotoine thanks for your help.