When I hear of or see a stock with a wrinkled finish, I immediately think it may be an old shellac finish. Many manufacturers used shellac on gun stocks, and many guns have been refinished with shellac. As shellac ages, it typically becomes dark, and it will also become wrinkled, in a way that is sometimes described as an alligator hide.
I have a 16 ga. Field Grade featherweight L. C. Smith that has a shellac finish, and I see no sign that it has been refinished. So it appears that Hunter Arms probably utilized shellac on at least some guns. Other original Smith's I have appear to be varnish.
A way to tell for sure is to apply some rubbing or denatured alcohol to a spot. Shellac dissolves easily in alcohol, but alcohol won't have much effect upon varnish, lacquers, polyurethane, etc. When you buy shellac in flake form, alcohol is the solvent used to make It liquid. It may soften the surface of an oil finish though. If the finish is shellac, the alcohol can easily strip the entire stock for refinishing, or with care, the dissolved shellac can be reamalgamated and evened out to dramatically improve the appearance. The surface should be well cleaned before attempting this, because dirt and grime on the stock will end up in the liquified shellac.
I have a G grade Lefever and a Baker Batavia that I bought very cheap because of their very ugly alligatored stock finishes. I instantly knew they had been refinished with shellac. As it turned out, the shellac had been applied right over the existing original finishes, and even slopped onto the metal and buttplate on the Baker. It was very easy to completely remove the shellac without harming the original finishes underneath. The shellac on the metal did a commendable job of protecting the case colors on the frame too What will always mystify me is why someone would decide to apply shellac over a perfectly good original finish???