Are hand throttles rare?

[boundstaffpress]

Tonight I'll try to get pics of the handle and handle shaft. My cable is not attatched, so I won't be able to get any pics of the OEM cable fastener, but would appreciate someone else doing so.

My father-in-law was telling me that he has several of this type of controller on the dash of his airplane. He said that the knobs have buttons in the middle. Push the button to release pressure on the threads and make course adjustments or turn to make fine adjustments.
Aircraft maybe another source for repair parts or non-OEM replacements.