I finally found a couple XM193 WECOM dummies (30x100B). Oddly enough, the dummies have different styles of crimping on the projo, and one is headstamped while the other isn’t. Also picked up some .50 BMG that I didn’t have yet: M8 API and M20 API-T (for really cheap; I may go back and buy the rest).
This one, with the darker brass, has a headstamp that read as follows, “30MM XM193 FAE 418 1968”. It also has a red sticker near the rim that says, “EOD INERT” and a red do-it-yourself type label on the projo that says, “MI-13.” I thought about peeling both of those off, but thought I’d double-check to see if they’re significant for some reason before I did that. Both stickers look like they’ve been on there a good while…