Originally Posted By: Geo. Newbern
I believe I've read that the "R" is for "reinforced" or something like that; presumably means stronger action. I think my 16ga Ideal is a 3R. Sadly, the sling mechanism is gone from mine. I bought an old .22 automatic made by Hi-Standard just for the sling which should be interchangeable, but because my stock had also been shortened I could not use it ...Geo

The R (Renforce) was intended to address the smokeless (Pyroxylee) powders. The 2R existed from 1899 to 1924.
Best regards,
WC-