Please consider donating to help offset our high running costs.
Here's my Seamaster 30 with such an "R" movement.
I also think that it is a replacement movement from Omega.
Interesting to see this thead revived once again. There does seem to be consensus that the most likely explanation is a replacement part but nothing concrete so far from what I can see. Reassuring to some extent but I guess on something like a Speedy a big impact on the value taking in to account the possibility of it being a franken.