East German Luger Value?

Yesterday I saw a badly mismatched luger with WWII parts. It was a good looking luger none the less. It had to the right of the side plate " Wach Regt. F. Dzerzhinsky" This was the regiment that provided state securityin East Germany. Dzerzhinsky started the KGB. The regiment is named after him. The gun also has " Staci and a number" on the grip strap and some other number that look like a unit ( maybe a lower unit of the regiment. Did not see any import marks. It was reblued, mismatched, but had to me interesting markings. I offered $650 and the owner asked $850. Do you think the marking are original and if so do they add to the value? What would be a fair price. Thanks for any help.