Here you go, pretty sure it is brushed 6061. Seems clear coated.
Just needs some decals, TLC and some quality components. Maybe I will use it for my Colorado bike. This frame is tight, as in stiff. There is no flex in that rear triangle. And it seems to be at least in the same weight range as my Centurion Prestige (another nice bike). This bike is a 56cm. No dents or dings but the center chainwheel is chewed up on a couple of teeth, odd, usually it is the outer that gets bunged up.
As it is sitting there it weighs 20 pounds and 10 ounces. Regardless of where it was made, the workmanship is clean and neat and the tubes are all straight unlike Cannondales of that approximate era which were crooked as all Hades.
J