I don't know of any. It took me some time to be able to tell C coum from C. hederifolium when both are in flower. C. coum has rounder leaves, boxier flowers and flowers later, but I find their flowering periods overlap.

I don't know what the Coum Corm is like with established clumps as they stay under ground and probably get much larger as time goes by. Hederafolium, however, definately enlarges into a smooth rounded purplish corm which sometimes blooms on the surface of the soil. The ones on the surface are about 2 inches or more across.

Cyclamen coum corms are round and smooth. They are slightly flattened and a greenish colour. They don't grow very large, at least mine don't, maybe slightly larger than a man's thumb. If you were to dig one up now there would be roots growing from the center of the base of the corm and maybe just a hint of growth starting at the top.