Hi Rusty, that's wiping solder, good stuff. All phone cables used to have a lead outside sheath. Any where the cables need a splice, the copper wiring that was spliced which had paper or later pulp insulation was coated several different ways.
This was covered with cotton muslin and covered with a lead sleeve. Depending on the size of the splice it may or may not have had solid lead end plates that were made to fit the size of the cables. This lead sleeve was soldered to the end plates by a means called wiping. Molten solder was poured with agood size ladel out of a pot that probably held 35 to 50lbs of solder. As it was poured it was caught on the bottom side in a large wiping pad to be held against the bottom of the sleeve. When the whole joint was hot enough. The joint was smoothed over to a perfect water and air proof joint. Then you did the other end.
Solder was also used for dipping twisted copper wire spliced joints in and then the excess was shaken off and waxed cotten insulating sleeves were applied.
Probably more info than you wanted.
ETA Yes I think most was 60/40 solder although they did use smaller pieces of 50/50 to as a sealing solder and make the joints shiny.
