In 1964 I toured the Resistol Hat factory, which is located in Garland (a suburb of Dallas), TX. Resistol was founded in 1927 and today sells more than 1 million hats each year. Resistol hats have been/today are worn by presidents (LBJ and Reagan), famous "Texas" personalities (George Strait, Tom Landry) and law enforcement (e.g. Texas Rangers and Texas DPS officers). The Resistol folks said that the number of Xs Resistol assigns to a hat indicates the quality/content of the hat's felt. Felt is generally a mixture of wool and beaver furs. Occasionally felt includes a beaver/ermine blend. Today, Resistol's hats range in quality rankings from 1X (lowest) up to 1,000X or more, with prices from $15 (for straw) to over $3,000 for a beaver/ermine model. The highest end hats are custom-made/custom-fitted for a specific wearer.
Every hat maker uses their own unique rating system in determining their X ratings - one hat maker's X system likely differs from another maker's system.
During my plant tour I bought a 10X Resistol hat from the "factory store." It sold at a 50% discount from retail price because there was a blemish on the underside of the hat band. Now, 60 years later I still have that hat, and it's in "almost-new" condition. I've had it refitted a couple of times (refitting requires a steam machine to permit the hat to be stretched and shaped). It is among my most prized possessions.
