This (and the cache submission form size dropdown, as well) is what I am basing the size on when I say that it looks like it would hold a regular geocoin:
http://support.Groundspeak.com/index.php?pg=kb.page&id=75
6.2. Containers Explained
Sizes
micro: e.g. 35mm film canister or smaller
small: Holds only a small logbook and small items.
regular: e.g. ammo box
large: e.g. 5-gallon bucket (about 20 liters)
other: See the cache description.
That is how everyone in my area lists them. Although I've seen maybe one listing saying their 35mm as a small. I'd just hope however it is listed if there is doubts the placer will say what to sort of look for.
