Good question Bruce. Because there's a lot more involved than just grinding off a few stamps and adding new ones. You have to be pretty proficient at metal work to do an even half way decent job at it. Then, you have to refinish the pistol to correct standards, and lugers, especially in the 20's and 30's were potentially subject to a variety of reconditioning/rework processes (the byzantine depot system that Ryan laid out is part of that story). In this case, what the base pistol was is anyones guess. You'd really have to have it in hand to look closely at any details that might (or might not) give away it's origins. With helmets, my guess is as long as you have the right make and type of helmet, refinish and decal away. In this case, it is a much more sophisticated process to fake something...there's a lot of potential missteps that can give away the fakery. And it isn't always the entire gun...sometimes just a barrel, or a slide or some minor piece. To do it really well is really an art form, or not. We've certainly seen a long list of folks in the K98k community that have tried their hand at such shenanagins.