Of course it has been reblued and it is not even a very good job, plus the gun was a mess before being polished!
Just look at the pic with the slide serial number; not only is the surface uneven, but the numbers are partially blurred, and the corners rounded. Plus Beretta used rust blue at that time and the gun was reblued using hot tank blue.
I could go on but there would be no point.
The gun is rare enough that if you could get it at a reasonable price (say $150) it would be worth buying, IMHO, and maybe using as trading stock if you encounter a better one. But at $300+ you would have to need a collection filler pretty bad.