For your consideration, I have a Vintage 1940s WWII US Navy White Dixie Cup Cotton Twill Sailor Cap Hat USN.  This hat has a several stains - appears to be a lot of storage stains that may come out with soaking.  Measuring the inside of hat rim, it is 21" or 54.340 cm.  This comes from a smoke free home.  I will be listing several vintage items so check out my other listings as I will combine shipping on multiple sales.