The shaft has a nut at the bottom end of it which acts as a lock nut to secure it to the linkage which is outside of the cab. The button itself has no lock nut. That end (the top end) is 1/8" NPT which is a tapered thread, which is inherently self-locking. There is a flattened spot on the shaft near the button which you can get a small wrench on to hold it while you unscrew the button. The underside of the button is hex-headed.
Now I must go outside now and enjoy the recent explosion of wild rabbits in my suburban neighborhood, which is a good sign that the coyotes have not moved in................yet.
Carl

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission