That is a hat rim. They were first issued as a 9 x 32 on the first 9N. Later 9 x 28 became an option. Later still the 32" was discontinued and 28" became the only rim available. With the NAA a 10 x 28 hat rim became an option.
The 32" rims are highly sought after and are worth some money. The wider 10" version of the 28" rims are also scarce, but don't seem to command as much money. The 9 x 28 hat rims are what most people are looking for. Prices remain firm at about $150 for a spotless example, down to $50 to $75 for a ratty one that needs repair. Brand new reproductions are NOT available (to my knowledge). In my experience, it costs about $40 to $50 to ship a rim from my home in Utah to the east coast. I did ship one hat rim to Hawaii and that was EXPENSIVE....shipping cost way more than the price of the rim!