So I was RAing GT2 today with Tails and got what I think was a perfect ring count of 189. The bonus plate gives me 10 rings, and I D:; submitting records only achievable with random elements isn't a gauntlet I want to throw down at the moment.
But maybe it isn't random, I think. I run it with Sonic and again get 189 and 10 free rings. Hm! I run twice more with Sonic and get 89 each and also get a ring each time.
Time for some scientific analysis. Here's the rundown, for all 2-3 of you who play the game :o
GT2(T)
189: Ring
GT2(S)
189: Ring
89: Ring
89: Ring
34: Sonic
40: Emerald
53: Sonic
54: Ring
36: Nothing
32: Tails
35: Blank, Ring
37: Nothing
AD2(T)
58: Nothing
37: Nothing
38: Nothing
33: Sonic
31: Tails
RW1(T)
53: Sonic
38: Nothing
54: Sonic
54: Sonic
RW1(S)
54: Sonic
GT2(S)
54: Blank, Ring
GT1(S)
40: Emerald
38,40 and 53 were consistent between the levels tested and both characters; 54 was consistent between S/T on RW1, but NOT consistent between AD2 and RW1. This might take a lot of runs to nail down. The hundreds-count seems to be irrelevant and the blank random, but it's hard to say anything conclusively yet.
These were all done using an emulator with savestates from either level select or midlevel. I'm hoping that doesn't contaminate the data, I'll do some more runs on actual hardware later to check.
Edit: Update - It looks increasingly like it's based on the ones digit. Latest GT2S data (all from inlevel saves)
90: Emerald
99: Ring
87: Nothing
85: Blank, Ring
88: Nothing
86: Nothing
93: Sonic
0:Emerald, 1-2:Tails, 3-4:Sonic, 5/9:Ring, 6-8:Nothing
The only thing it isn't consistent with is the 54 ring bonus on GT2, which is odd considering 34 gives Sonic... so there's probably a monkey wrench in the works somewhere, but at least for these levels it still seems pretty close.