The picture below shows a larger view of this Old Enameled Metal Buick Authorized Service Advertising Employee Pin. This tie tack type pin is not dated and the year that it was made is unknown. It is enameled in red, white, and blue and is marked on the front as follows:
BUICK VALVE INHEAD AUTHORIZED SERVICE
The metal back section is included. The pin measures about 3/4'' wide. It appears to be in excellent or better condition as pictured.