...I’d personally stay away from hats marked S,M,L,or XL. They definitely are not accurate for sizing.
No doubt! I have a couple of Stetson hats up on eBay and one is marked "M" (measures out to 7-3/8) and one marked "L" (measures out to between a 7-1/4 and 7-3/8). Maybe Stetson added "XL" to the range at some point after the "M" was manufactured and adjusted the others down. Or they were just not very good at what they were doing in this time frame.