Weaver offering, A, non powered B set. There was an upgrade, to powered B unit. There was also available, additional Powered A units. Limited quantities. Pennsy, Long Island RR, ran A B A sets. They did not MU with other units.
The antenna rail was part of a Pennsylvania radio phone communication system, early, before walkie-talkie, or cell phones. My foggy head thinks the Antenna/phone system, on board, talked to the wires, on poles, beside the track. I could be wrong, and often. Mike CT
A comparison of unit lengths. Top shelf is a Weaver E8 set. BP20 bottom shelf.