The two receiver ring diameters were 1.30" for the "small" ring and 1.40" for the "large" ring. There may have been a third size; Olson states that the receiver ring of the G.33/40 is 1.295" but that is close enough to 1.30 that the difference is more likely a matter of manufacturing tolerances than of a truly different size.
One point of confusion is that we usually associate the large ring with the 98 action, and the larger ring was part of the 98 design, to strengthen the receiver. But there were rifles which used the 98 design in other aspects but which used the small ring, usually as a weight-saving measure. The G.33/40 was one of those; the Kar 98a was another, as well as early military and several commercial models.
There are also variations in the length of the receiver ring, and several lengths of action, especially when commercial Mausers are taken into account. Stoeger listed 20 different Mauser Oberndorf actions, with 8 different magazine lengths. It is not indicated how many actual actions there were (as opposed to variations in receiver and magazine box machining), but Mauser, like most other gun companies of the time, would make what a good enough customer wanted.