Model Train Journal

https://www.ebay.com/itm/Lionel-2343-AA/174316145804
I cannot ever remember seeing a plastic shell like that. Acid? Heat Who knows. The frame on the other unit is really bad...along the shell line. Big corroded divot below the rear porthole. Tank. Pickup assemblies different on each. Ladders missing one one unit's trucks. One rear ladder gone. Sideframes are too nice. Came from elsewhere. But, they're freshly GLOSS clear coated! Gotta be worth it for that, even if nothing else is.
Opinion.

Heat gun. I think they tried to strip the paint?

Maybe. The top of the other unit is eroded towards the rear. Like they laid is a caustic bath, ate the frame, shells. Strangest one I've seen.

Not many plastics are affected by acid/caustic liquids. Solvents are another mater. It looks like there is blistering going on under the current paint job and 50 coats of Future floor wax used as a top coat. Even the damaged areas shine!

Thinner would eat into the plastic......been there, done that.