Finish questions

I got an 84 musicman Sabre, and I can’t really tell if it’s nitro or polyester, George Fullerton said that the polyesters cracked at the time but the neck is also extremely yellow. I’ve also seen some bases from the vault from the same period and those finishes are hilariously cracked. Wondering if it’s nitro or polyester.

Since it’s an 84 it can possibly be that the neck was a pre eb neck that had been finished by then, the string tree is in the eb location though