Since I’m on the subject and have dug this stuff out, I might as well post the Marble adaptor cartridges. I have three types. the top three rows are the most common type with the slits. All but two of these are marked MARBLE’S USA and the code number. Two of these simply have the caliber of the rifle cartridge and the caliber of the pistol cartridge that is to be installed.
The bottom row are two different types of adaptors. The ones with the snapclips are marked MARBLE’S but one has the number and the other the caliber. The final two have a cutout in the side for loading.
I have had these about 15 years, and find them interesting but don’t know anything of the history.