Telescoping cups:  These shots probably predate the aluminum two-parters.  They're constructed of a series six or seven chromed metal rings that create a two-inch drinking vessel when expanded.  They could be collapsed down to about 3/8th of an inch, presumably so that they could be slipped into a vest pocket.  Branding information was embossed or inscribed into a metal cap that clipped over the base and held the shot closed.