SANTIAGOP23 posted:
It is a mail car destination card holder used when mail / express cars were sealed and carried to a specific location. Not used when cars were worked en route as the information would have not been accurate.
I worked for the PRR / Penn Central on mail and express cars and we used them. For cars that were worked en route they were not used. Just for solid mail to a specific point. Baggage cars, express reefers, and express box cars had them.
As I recall from the 1960's most cars just had the outer assembly - not the inner pieces but my memory could have faded.