It's kind of hard to tell from the pics if the shiny silver spots are solder, as jOe mentioned, or if they are just spots where the barrel browning and patina was removed by something acidic. You might try using a Q-tip to dab a little acid solder flux or salt water on one of the larger shiny spots, and put the barrels in a humid spot for a couple days to see if the spot gets rusty. Solder won't rust, but bare steel will.

Voting for anti-gun Democrats is dumber than giving treats to a dog that shits on a Persian Rug