Lacquer, used it for years.
Easier to wet sand and polish than urethane.
Can be sprayed over with urethane.
There's still lots of cars at the shows, (mostly old rods)
Painted with lacquer.
Yes you can clear coat it.
Some say it has a finish todays paints can't touch.
REALLY easy to touch up.
Bad news the solvents used to spray lacquer really suck, that's why the industry stopped using it.