Need help with a white layer of paint on IMP liner, maybe some sort of primer/base coat?

[Sneaky]

Hey folks. I’ve found an IMP liner (very poorly) repainted over with crafts paint, and I have been carefully stripping it. There is some sort of white base coat applied over the exterior fiber of the liner, and I’m curious as to what it is, as I plan on selling it. 
 

My best guess is it acts as a base coat or primer for the OD paint. 
 

I’ve attached some pictures below, first two are 30x and last is 60x. It appears to have been brushed on, as there are discernible brushstrokes.

 

if anyone knows what’s going on here please let me know!