Tach time - nominal RPM

As discussed in this thread, the tach time on a mechanical tach is scaled to some nominal engine speed. Does anyone know what Lycoming recommends for this engine speed? This is the speed at which running the engine for one hour would yield one hour of tach time.

Thanks...

-Rob

This may be wrong, but I thought factory plane tachs were setup for rated RPM. Sound right?

Seems like it was an odd number. For some reason I think my IO-520 engined Bonanza was 2566 rpm. Don't remember what Lycoming uses. I just set up my Dynon for 2500 rpm.

on my old 172 with a continental, one hour @ 2500 rpm was 1 tach hour.