... good stuff P32.
I haven't touched Mauser's yet, therefore, I have no idea what people mean by "large ring".
Small ring Mausers are those pre-1898 (pre Gewehr 98) Mausers that had a smaller diameter receiver ring and two locking lug recesses. You can easily recognize them as the receiver rail merges smoothly into the receiver ring (front of the receiver just prior to the chamber). Examples include: Argentine M1891; Chilean M1895; Swedish M/94, M/96, M/38; Spanish M1893, etc.
Large ring Mausers are easily recognizable because they have a step from the receiver rail to the larger diameter ring. Internally, they have recesses (or races) for two bolt lugs and one safety lug in the rear receiver bridge. Examples include: Gew98, Czech Vz24, K98k, etc.