Arcade’s wall mount coffee grinders and mills use some type of catch cup. For example, Crystal No. 3 mill uses a glass receiving cup graduations marked at tablespoon levels, and X-Ray grinder uses a detachable cast iron cup.
A lot of the antique coffee mills being sold on eBay or other markets come with a replacement receiving cups. If you want the original matching cup, you must know what it looks like. If you need help with identifying the matching cups, please let me know. I can tell you what kind of cup each Arcade coffee mill uses.