I don't think they could do that combination of a .410 and a 20ga. There's to much difference In the OD in the bores. The gun I've aquired came from the factory as a 1E 16 ga and was sent back to LC Smith in 1940 and probably fitted with the 2nd set of barrels that are 20 ga. Both sets of barrels are 26" in length and both sets are ejector barrels. John Liles and myself have sent a lot of pictures of the gun with both sets of barrels on and off the gun to several LCSCA members. I'll post them for all to see in the next few days. Hope ya'll will be sitting down !