Voenkomat Medal Ring Variations.

[Lapa]

You've got the right idea, unless one could have access to the Mint archives :(

There is a clear evolution of the shape of the ring:
. flat with a funnel-like opening on both sides (this is the way it was struck, it is not a flat tab that was then pierced)
.. hard-angled internal hole
.. soft funnel-like hole
. rounded (two varieties):
.. thin ring
.. thick ring (several sub-varieties)
... regular circle, fully circular hole
... regular circle, noose-shaped hole
... indented circle at the base, circular hole
... indented circle at the base, ovoid hole

Marc