R over R could most likely be a repair, i.e. the letter being repunched into the die due to wear/infill or similar. However, there are cases where the die was wrong to start with, is repunched, and quite possibly these might be classed as varieties. For example, there are some 1882 pennies where the first 1 in the date (done by Heatons of Birmingham remember, not by the Mint) is slanted ("retrograde") and was repunched before striking - this is regarded as a variety though possibly not collected by many.