While talking about old splice caps here, I just removed an old one from a 40's house. It was a brass? crimp on the wires. UL listed for 10-18 AWG wires. There were 4 dents (one on each side) so I guess it was sort of crumpled on the wires with a special tool. Over this was a black rubber cover shaped like a wirenut.There were 4 bumps (to fit in the dents?) inside. At the end was a B in a triangle (Buchanan, I think) and the number 2005. As an extra security for the insulator, there was a red ring slid over the cap. I think it was original. I has to cut the crimp off though, so I was left with some 4" leads from the box.
Very labor intensive.
Thinkgood, is there a spring inside? I guess even if there was, it has rusted out from being buried for years.