Hi Igor...
You have quite a mix of luger parts in one luger...we would call this a parts-gun and it is in a shooter (not collectible) category.
Your luger may have started out life as a 1917 DWM artillery or maybe a 1917 Erfurt (either artillery or 4" barrel model). Somewhere along the way it got a rare Bulgarian stamped read toggle link, from another pistol or parts.
It has also been dipped blued and many of the small parts that should be straw colored are now blued.
What serial number does the gun have and how many 2-digit numbers do you see on the small parts that might match up to the last 2 numbers of the full serial number ?
Your magazine is not from the WWI era but probably from the 1930's or WWII era. It is desireable in that is is not stamped with proofs or serial numbers. To luger boosters and forgers, this magazine has value and they like to get their hands on them so they can make "rare" magazines out of them for big $$'s.
Some 1930's Mauser commercial luger collectors seek them out as several of such lugers came with un-numbered or un-proofed aluminum magazine.
I would guess $ 400-600 price range...you might be able to sell the magazine by itself for $ 150 or so...
I have lightened up your photos a bit some other members could see more detail and be more of help than I :
