There is a fair amount of
Machine Doubling going on here. At 10 o'clock on the inside curve of the 9 and the 0 , as well as the MM.
Could all this have covered up the rpm ? Probably not . There is a northeast direction to the secondary MM of rpm#1 that isn't evident in the OP's photos
Edited by stoneman227
08/29/2019 08:29 am