Among the more obscure chapters in comic book collecting are the special advertising inserts included in comics shipped to overseas military PXs. I have several books with Mark Jewelers inserts myself, and didn't know what to make of them for the longest time. Like a lot of ads in the 1970s, they were geared toward adults, and not the children that are stereotypically the audience for comics. I eventually had them pegged as military base exclusives, but the "outside of the U.S." aspect was a wrinkle I hadn't considered until recently. It does make perfect sense.
In looking into Mark Jewelers, I discovered Military Insert Mania via this message board thread. I learned a whole lot more about these inserts from those two sources than I had in all my years of collecting and stumbling across them by accident. But there are still plenty more mysteries about these shadowy, hidden "variants." Chief among them for me is how the military insert arrangement came about in the first place. I'm also curious as to why it was Mark Jewelers that carried the banner for something like 20 years.
Mark Jewelers (also H & R Sales, but apparently the same company) was located at 9041 West Pico Boulevard in Los Angeles, California. I stress "was" here because it looks as if that location has been swallowed up by Bais Chana Chabad High School, a private, Jewish, girls-only school. I can't find any record of "the" Mark Jewelers still existing, though it's certainly possible that they do. Considering the ads disappeared in the early 1990s, I wouldn't be surprised if they gave up the ghost around that time.
Regrettably, that's all I know for now. I'll probably be making further inquiries as time and interest permit. I can't speak for anyone else, but I'd love to know more about Mark Jewelers and why they considered comic books an effective tool for reaching their customers for two decades.