2” = 50.8 mm
1 15/16” = 49.2 mm

I believe I owned the two largest 50s. There is only 1 known of each. A guy bought a binder of antique photos. The last page had 8 or 9 ivories attached all large and all rare.

Kenny had a gorgeous 50. I don’t believe it was as large

I left “Big Blue” in the scan for size comparison.