Advice, please!

[drobe999]

I'm trying to come up with a reasonable offer on this gun... belonged to the father of a friend, who brought it back from WWII. The owner died about 10 years ago, and his son wants me to help him sell the old Luger. I'd really like to buy it, but the more I dig into it, the more I'm starting to realize it may be a little out of my price range. It appears to be in great condition; wear doesn't seem too bad considering the age of the thing. Can't find a date stamp where I've seen it pictured on other examples so I'm wondering if it's one of the older ones. Got some pretty good pictures of the proof marks and serial number. All the numbered parts seem to match except for the magazines (one has a wooden end, the other looks like aluminum). I took the grips off, but did not see any numbers stamped on the inside of them.
I am curious as to what the "120.R.M.G.3" stamped on the front grip strap means.
Any help you guys here can provide will be greatly appreciated!