Black Rubber 3/8″ID steel post sleeve, stand 1/2″ Tall.
Found mainly on Data East, & Sega Pins.
Fits onto the lower half of the thin metal posts, as pictured.
From what I can tell used a back-up should the 3/16″ID white rubber wear out, or break prior to overhaul.
As found on titles such as : Batman, Hook, Rocky & Bullwinkle, Checkpoint, and more.
Data East 545-5151-00, 545-5190-00