This is the smaller flywheel for the later models R69S:

~214 mm versus ~226 mm

4 kg versus 5.6 kg

Markings on flywheel:

OT 

S = 9° before OT

F = 39° degrees before OT

These markings are correct for R51/3, R67/2, R50, R50/2, R50S, R60, R60/2, R69S (> VIN 658 164)

R67: 

S = 6° degrees before OT

F = 36° degrees before OT

R68, R69:

S = 12° degrees before OT

F = 42° degrees before OT