I just looked at 2 smiths, both 8 3/8 bbl, one is a 17-4 22LR SN 89K92xx and the other a 48-4 22MRF 86K61XX.
Reading top post it talks up to a 17-3 and then in next paragraph goes to 17-7.
Where do the 17-4 and 48-4 come into play