All the post war German guns had a quality mark on the right side of the rear lump.(or was it the left?)
Either a "2" or a "1" in a diamond or a fancy "Q".
This mark does not seem to be directly related to the guns grade , but rather the overall fitting polishing etc.
That said my BUHAG has a "1" but is better finished than most "Q" marked guns I have seen.
Judge the gun on its individual merits.

GDU