6 x 14 plate with 2x12 plate molded on top and metal contacts on the bottom identification Needing help identifying this part as I was offered a small bag of vintage train parts and this come with some very unknown parts to me.

I just recently got out of a 33 year old Dark Age and have zero experience regarding vintage trains, so hoping somebody could jump in and offer me a hand.
Part# BB0054 - Electric, Train 4.5V Battery Car Roof. 

(But Light Gray in color.)