Ben-Hur Trailer Unknown Brake Part? (4ea)

OFFICIAL NOMENCLATURE: ?
PART/STOCK NUMBERS:
GOVT GROUP #:
APPLICABLE SNL’s:
QUANTITY REQUIRED PER UNIT ASSEMBLY: ?
NOTES: These unknown parts came with the other Ben-Hur trailer parts purchased long ago. As can be seen, they have been poorly stored and exhibit rust and corrosion. They measure 5/8″ long x 5/8″ wide x 3/16″ high. The hole in the middle is also 3/16″ in diameter. The projection on the side is about 1/4″ wide. Let us know if you are able to identify them. YOU ARE BUYING 4EA.
OVERSIZE Y/N: NO
INVENTORY CONTROL #:
SKU:
PLEASE CHECK YOUR MANUALS, INSPECT YOUR EQUIPMENT, ASK THE EXPERTS BEFORE BUYING; THESE ANTIQUE PARTS ARE DECADES OLD. NO WARRANTIES ARE IMPLIED OR EXPRESSED. I DO NOT ACCEPT RETURNS.