Not an R. Probably a lightly struck D or an E - which is 1952/1953 and matches the serial number. There is crossover in this serial number range to both years, I tend to go with the later year under the assumption it's quite possible that Savage didn't get around to switching to the new stamps for a couple of months. I find that more likely than they had 13,000 or more receivers stacked up in a queue and they did them out of order.
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