In cleaning up what I believe to be a '71 383 warranty block (blank VIN pad, never stamped), I found some interesting markings on the data pad by the distributor

The G383 is straightforward, as is the 12 14 date (10/70 casting), but what are the punch marks below that?

It appears to be 'F' 'R' (factory replacement?), but it's sloppy enough that it could be anything.

Insights would be appreciated.

Thanks in advance