Interesting Re-Work with M/A proof

Hello members,

this weekend I was visiting relatives for the holiday and met some one at a local gun store that said they had a luger that they'd owned for some time and would consider parting with. He said that other collectors in the area had inquired about purchasing it for years but he'd just held onto it. It's apparently the only luger he owns. I followed him to his house to look it over.

At first I thought it was simply a parts gun but then I noticed an interesting proof on the left side of the receiver - a M over A. Here are some of the particulars:

Military proofing, 1920 on receiver with no other date, S/42 toggle, mixture of strawed and blued small parts, rebarreled, numbers matched, upright crown/n on left receiver, stock lug, hold open is missing, wooden bottom magazine is chipped.

The proof is exactly like the proof on page 2 of Jan's "Weimar and Early Nazi Lugers" which designates acceptance by the German Navy. I didn't know enough about the proof to make an offer so I told him I'd like to think about it. I looked the pistol over for other proofs or unit/property marks and there were none. It's action was smooth and it "took down" and re-assembled smoothly.

Does this pistol have any collector value and if so, what would be a fair purchase price? Condition is 90-93% with a thumbprint stain on the side plate.

Thanks for any information!

Richard