The picture below shows a larger view of this Massachusetts Bay Transportation Authority MBTA Employees CreditUnion Advertising Pin. This brass pin is not dated but it is believed to be from the 1990s. It is a tie tack type pin and the back section is included. The pin is marked as follows:
MBTA EMPLOYEES CREDITUNION T SERVING FOR OVER 60 YEARS
The pin measures 1'' wide. It appears to be in mint condition as pictured.