The N denotes NEF, the R is the year of mfr, 2001, that info can be found in the Centerfire forum FAQs. If it was sold as a Huntsman only, it's an SB1 frame which shotgun barrels can be fitted, but not rifle barrels. If it was a combo or an accessory barrel fitted to an SB2 rifle frame, the only way to know is call H&R and they can tell by the serial number what it is and how it was sold. You can compare it to the frame pics in the FAQs and see the differences between the SB1 and SB2 frames, but the best thing to do is call H&R and ask em what barrels can be fitted to it.
Tim
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