The Eberhard Faber Co. often stated that their clamp eraser would “outlast the pencil”, but they still saw fit to provide replacement erasers. These small Mongol refill boxes contain three flat, red erasers and one metal clip:
The question is whether these erasers were considered “Mongol” erasers (i.e. part of the Mongol line along with the Van Dyke, etc.), or were simply refills for Mongol pencils fitted with a clamp eraser. For example, there was the pocket Mongol pencil that came with a clamp extender:
Later on there would be mechanical Mongol pencils similar to these Permapoint pencils, which featured a clamp eraser:
Previous boxes of clamp refills each had four erasers (instead of three) and a metal clip:
Perhaps the four-pack had one refill too many. But by specializing the packaging (i.e. calling them “Mongol” refills) would consumers have known they were compatible with any of their clamp-related products? I suppose that the store display likely explained as much.