12ga and smaller shotgun barrels, and low pressure rifle barrels, 22 Hornet, 357mag, 44mag, trapdoor 45-70.... if you can get em to fit. Modern SB1 and SB2 frames aren't marked either, but they weren't made until 1987 either, yours was made by H&R Inc that went out of business in 1986, there were no SB designations on their cast iron frames. See the build year list in the FAQs and Help sticky.
Tim