The patent appears to be 282,546, by Edward R. Mason, of Des Moines, Iowa.
"Adjustable and Detachable Arbor for Grindstones"
Unfortunatly, it refers only to the metal parts ...
(A search of the inventors name brings up some interesting, if unrelated court cases, Edward was a bad boy ;P)
"It's a Maytag" LOL
Edit: I am not certain there is only one Mason here, But, there are also interesting references to a fellow who shows up in relation to Mason Motor company (spun off from the Maytag-Mason spinoff from Maytag co, when they gave up on making a car to make just washing machines) , and also gave up competing with Duesenberg...hmm
circa 1911)