2500/2187

Pondering "bearings", and thinking about creating 5-limit Fokker
blocks for 4375/4374 to temper, I was led to consider the (more or
less) comma 8/7 * 4375/4374. This is a curiosity, with mapping
[<1 2 3|, <0 -4 -7|] giving a temperament with a secor as generator
(7/72 being the first poptimal generator we find.)

Maybe 6561/6250 could be useful from a bearing point of view also,
not to mention 15/14 * 4375/4374, 250/243 = 36/35 * 4375/4374, or
20000/19683 = 64/63 * 4375/4374.