Actually, here's the skinny on Chrome Plated Lugers. I did some research on it when co-worked told me he still had his dad's chrome plated Luger that he brought home from the war. He had been cherishing it, and hadn't even touched it in decades.
NO (I repeat NO!) Lugers were chrome plated by the Germans. They all had standard black oxidized coatings.
Some soldiers, returning home from the war, thought it would help preserve their prizes from rusting if they chrome plated them. Several chrome plating companies seemed to specialize in handling this. Some of the chrome plating jobs were so botched that the parts were all chrome "welded" together. The platers didn't take those guns apart, and plate the individual parts, they chromed the entire gun assembly. Just a solid glob of chrome. I know, welding isn't the right term. Just wanted to give you the visual.
Typically, the chrome plating did little more than make a lot of parts very fragile. Springs, extractors, and the like. Often, the inside of barrels got chromed also, making the lands and grooves very inaccurate.
The collectible value of the chromed guns is most often less than the value of the nazi leather holsters that came with them. A Luger in good original (oxide finish) these days is about $550 to $1200. A chromed one is barely worth $200.
I convinced my co-worker that his dad's Luger was a shooter, not a collectible. A few parts broke right away, most likely because of the embrittlement from the chrome plating. Fortunately, there are replacement parts aplenty for these guns.
He now shoots it regularly, and is taking up reloading 9mm Luger (the round that we 9mm shooters use is STILL usable in the old Lugers. ) to support his new found joy. He leaves the leather holster in his safe, and carries the chrome plated Luger in a plastic carry case to the range.