About all you can tell about the frame is who made it...N= NEF and when S= 2002 in your case. The barrels are marked SB1 or SB2, not the frames. If you have a barrel for the frame, the last 3 digits of the serial number will be etched in the underlug, if it's a shotgun barrel, most likely it would be an SB1 frame. The only true way other than a matched factory fitted set, is to call or email H&R and give em the serial number, they'll tell you what barrels can or can't be fitted to it.
Not being overly knowledgeable on Handi Rifles, it seems it would be logical to stamp the receiver as to s = shotgun or r = rifle. Since it is the receiver that is the weak link and no one will be firing a rifle cartridge in a shotgun barrel but certianly could fire a rifle cartrige in a rifle barrel on a shotgun receiver.
Just seems logical to me but ****, I don't know beans about anything.
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