Hello, and welcome to the forum. It's most certainly a re-blued pistol, and so was a good buy as a shooter. It may have been dip refinished (this is hard to judge without the pistol in hand) and the work looks like it was properly fitted, which would point to arsenal work. It may have been a captured pistol, redone in the East after the war. (Russian or East German).

The single magazine base was ground down and renumbered.

So, enjoy it and shoot it regularly. These are very well made Lugers.