The original style mechanism used in many antique older style 4 leg wood office swivel chairs.
A 13 1/2" length mechanism when measuring length from hole to hole.
Bell is a 4" diameter covering the top of the 4 leg base hub plate and not removable.
The rails curve outwards at each end, as was the common style.
Front to rear hole length 13 1/2".
Side to side slot width, 8".
Acme Threaded post 1" dia x 9" tall, 3" unthreaded.
Ships complete as pictured.
Antique replacement mechanism
Measured hole to hole
1" dia Threaded post
Manual type