I am having trouble figuring out what this finish is on this mid-century piece of furniture. I want to repair it. I thought it was nitro cellulose based on how brittle it was and the period it was made. I removed a chip and put it in lacquer thinner, though,band it didn't dissolve. It became springy in lacquer thinner but not gummy. No effect of DNA on the finish. Could this be NC that's just old enough it won't dissolve anymore? Or am I looking at some varnish?