Geoff,
You are badly mistaken, and the people who imported the Siace you own broke Federal law, plain and simple. #479.102 of the National Firearms Act, Title 27, CFR chapter II is very clear on this. The model, caliber or gauge, importer, manufacturer, importers address, and, in the case of imported firearms, where the firearm was made, have to be engraved, cast, or stamped at least .003 of depth and in letters no less than 1/16 of size. It has to be placed conspicuously, and be on the frame, barrel or receiver.

I've imported guns for years, and if I could have left it off, I would have, plain and simple. Why anyone would think manufacturers would spend money to put the information there unless it was required under penalty of law is beyond me.
Best,
Ted