I don't see what would be the problem with making an accurate reproduction. I don't know if the design of the weapon is copyrighted, but I doubt it. Therefore, the only illegal thing would be to sell it as an original (if you buy one as an original, and you are in good faith, legally the dealer must give you a real one in exchange for the repro).
Of course, if symbols are represented that are illegal to reproduce in certain countries, the weapons can't be sold here...
It is possible at least some of them are originals. After all, the weapons are quite robust (they'd have to be

). Compared to some of the groups buying original German tank the prices aren't really that high either...
Christian