In the original R68 parts list (1953) the flywheel is shown in the exploded view of the same model as the R51/3 - R67/3 flywheels. (the ignition timing marks are different though)
R68 flywheels also appear to have been made with the design of the later /2 models.
I assume that these flywheels were a precursor in the transition to the R69.
