Here's an interesting article on the CoinWorld website about the actual definitions of medals, medalets, medallions based upon size.

Medals size article

I do not believe that a distinction between medal, medalets and medallion is really necessary and useful. A distinction in size by millimeter or inch is more precise. An introduction of medalet and medallion in my view will increase confusion, because in German language a medallion is a nice piece of meat (Filet) at the same time.

It would make much more sense to have different words for the type of medal that is awarded (honoring some merit), and the type that is made for the mass market. Another possibly relevant distinction is "Medaille" vs "Plakette"; the latter has one designed side only and is usually attached to a wall. But three different words, just based on size differences? Sounds odd to me.

Christian