I have cleaned the outside of the barrel(s) on my shotgun.
Here's what I found, LAMINATED stamped on the top of the rib, and not shown, but 12 on the bottom.
I got the LH nipple out, using a LH twist drill bit and cleaned the threads with a 1/4x28 tap. They now look pretty good, the RH not so good. The barrels are still plugged. I don't believe they are loaded though. The complete barrel(s) have soaked in Evaporust for 24 hours, twice so whatever is in them should be saturated, and non-flammable, I hope. I have sharpened a 1/4" metal rod to a chisel point and drove it in, trying to be as gentle as possible and still get some results. There was some dark specks that came out at first, but not enough to open them up.
I suppose I'll pour the barrels back full of Evaporust and soak them some more.