Interesting!
I expect there are a lot of .30 Luger guns in the world, but relatively few imported into the U.S. For instance, it seems to me that Beretta makes--or at least used to make--a version of the Model 92 in .30 Luger (Model 98?). I wonder if they've ever been imported here?
For my part, I have a .30 Luger BHP. It's a very fine gun, but apparently scarce in the U.S.