Hi Doug,
There were a number of companies that made this type for the Pennsy. Does the lantern have a vent chamber in the center of the pot? If so it may have been made by Plume and Atwood in Waterbury, CT. They didn't mark the lamps other than the burner assembly. You can check by removing the glass chimney and looking at the top of the fount baffle.
The lamp mounted to the wall with a plate (approx 3"X7") that had two curved fingers that came out horizontally two inches. The end of the fingers had threads on the end for mounting nuts. The fingers fit into the slot in the back bracket, one near the top and the other at the bottom. The PRR normally didn't use reflectors on their caboose (cabin) lamps.
Stewart