Back in April of 2016, I wrote a blog about cast iron skillets with factory concentric grind marks - shown in the photo was our inherited grandmother's #8 Wagner. The Wagner had just been restored and seasoned.
Well, here it is a second update years later. After regular use the concentric grind marks can barely be seen - the surface has seasoned nice and smooth. Do not be afraid to buy 1950-60's pan with grind rings!... they will work just fine.