Nitro was first in amerikan industrial laquering, if i remember right. It also was the standard laquer for cars until 50' (?), thats why gibson and fender use it in the past. It was there and it was cheap. Some of the 7ender colours direktly refers to car colours..
Gibson was clever enought (or just grasping? ), not to chance to poly and i dont think, they now ever do.
I dindnt mind, if a guitar is poly laquered, as long , as the neck feels allright to handle.
Sadly, poly dindt bleach or gilb like nitro, also it doesnt work. So it wouldnt chance the colour, like old nitro laquered guitars or the pinkish bindings on newer ones did.
This 79' Aria P2 TS 400 have poly laquer, its one of the best handling guitars i ever played and looks nearly new from 1 meter distance. You have to take a deeper look, for registering all the fine scratches and few dings, which tells you, she isnt a virgin
and yes, i like photos