A Gew98? Kind of has to be a 98k..
As to dot they seemingly were one of the firms that were a true "manufacturer" and not so much an assembler, like most of the German firms, I can't ever recall not seeing a "dot" barrel on a dot rifle, and they didn't seem to contract out barrels like every other fricken mfg in Germany proper. (obviously a product of their pre-war capacity/vz program).
Anyway, I suspect your "R" is actually a two part letter and the other is below the woodline?
90-99% of observed dot's have a dot barrel (dot shield/e63/two letter code which surely represents some lot number, - very likely a steel lot identifier as every other firm since 1880's used a similar system to identify the steel source- it was easier in Imperial times as there were only 3 big mfg) Anyway, only reason I bothered to reply to this question was the "possibility" there was a sub-contractor rather than the normally seen dot barrel?
S&S/Sauer is a bigtime known barrel maker, Imperial times forward they made oodles of barrels and were a prime contractor for them, the had a funky script "ce" which as often as not the "e" is mistaken for a "R" hence my reply.. 1944 saw an end to Sauer in the 98k business so even though a longshot of astronomical proportions it did cross my mind (hell anything's possible after the swjXE sale?)
Do some pics or if that is not a possibility, is there a "dot shield" if so I just wasted 5 minutes of typing..