Advice needed on prospective purchase

[adlerauger]

I've got my eye on a Luger that I need your collective advice on before jumping on it.
It's an Erfurt, marked 1921. It has no lug on the back strap, and it has the unit marked on the finger side of the grip's back strap. ( don't remember unit info )
A hurried look showed it appears to be all matching serial numbers but didn't have chance to look real close. Now, that's the good news; the bad news is, it has been re-blued! However, I can't see why it was, because all the edges are pretty sharp and clean and there's no evidence of pitting. Maybe the prior owner didn't like a Luger with a "patina" finish???
Mag's wood bottom, but not numbered. From what I've found digging around on the net leads me to believe this is an earlier ( 1912?) Luger??
The shop it's in wants $750.00 for it, but is willing to soften that a bit, plus he's open to trade. I'm going back there this coming tuesday so any and all advice is welcome.
Thanks in advance,
Adlerauger