When you start exploring the world of vintage cast iron cookware, different finishes to the pans cooking surface will be found... makers had various levels of machine polish grinding or none at all..
Some pans were left as-cast... the cook surface is rough and bumpy like sandpaper. As it is not smooth, this is not a great surface to cook on and hard to season. Not a good pan to start with, as it may discourage the new cast iron cook. Look for a smooth interior pan.
Smooth pans were generally stone polish ground with machines. Some pans were so finely ground smooth, they are works of beauty and are like a black mirror. A less labor expensive polished pan will have concentric spiral rings - like the pans in the photo. These pans should not be discounted, though. With seasoning, cooking and time a nice dark smooth interior will result.The pan on the left is a Wagner from my wife's grandmother's estate... after cleaning, seasoning and cooking for a year, the rings have faded to the background. We have cooked many nice meals with this family pan and kept the loving Southern tradition of a grandmother carrying on.