George is absolutely correct about the proof mark on the side plate. The proof mark would be in front of the two digit serial number and the same size as the fourth proof proof mark on the right side of the receiver. I can see a serial number on the rear sight that, with some very close eye balling by me, looks like the proper two digit number. That suggests that the weapon has NOT been rebarreled. While there is a serial number on the rear sights slider and in the proper location, I could not make it out.
The Locking Bolt has been poorly restrawed and lotsa metal has been removed. The grips look nice. Look under them the see if you can find a two digit serial number and an Erfurt proof mark. Be careful though. It is easy to break off the little finger at the top right just under the safety. The wood is pretty old and dry. Remove the mags and, very gently, pop the grips off from the inside.
Lets see, is there anything else. OH NO!!!!! Not a Gibson guitar!!!!!! Three years ago, I sold a Harmony for $1200. It even had a melted rest on it. I did throw in three picks to seal the deal though. And that was before I got onto Ebay. I don't know about your guitar, but in the era of my guitar, the Gibson was the better guitar. Oh well, now you have a real neat and classy Luger to shoot yourself in the foot with.
Big Norm