Acrylic lacquer sets by the solvents etc drying out of it.
2 pack (ie 2K) is a 2 part mix of 2 chemicals (think.... like `araldite' epoxy) and a chemical reaction then takes place, the result is a polyurethane coating.
This stuff is pretty much the same as the polyurethane gelcoat on a fibreglass boat- it's immune to acids too.
I used to work for a company that made truck concrete transit mixers back in 1972, they were painted in 2 pack even then. Still are. They wash them down with acid to get cement off.
It's tuff stuff.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
