Does OG Competition mustang ?

Hi I was hoping I could get any info about a 69 mustang competition bass that I have I’ve heard that the finish is poly but on the headstock is nitro I’m %99.99 sure it’s all original but the finish does look different on body to headstock wether it’s a thinner coat on headstock or is it true about it been nitro and poly any info welcome thanks
 
image.jpg
image.jpg
image.jpg
image.jpg