Picked up this signal and previous owner bought it at a Carlisle PA auto swap meet and he "thinks" maybe it's B&O but I can't find anything that looks like it in online searches.

Roughly 24-30" square, looks like bottom and upper left are fixed red with a red lens inside and clear on top. Would have to look over the upper right again. Case is aluminum. It is missing an outer lens, I need to check the box of lenses that came with to see if one of those fits.

I can't find anything on that Chock flag either, but we know where that came from. (all I get are pictures of newer devices)

Accidentally found the right search to find out it's a US&S tri-light similar to some used on the Pennsy outside of the corridor. Possible others used them too. Probably no way to track down what road it came from.

I have been all over the former PRR and much of the former B&O, and nowhere do I recall seeing that "tri-light" design of signal in use. Both roads were loyalists to different forms of the position-light signals, and even if I throw "dwarf signals" and the like into the mix that's a signal type I've never seen in former PRR or B&O territory, except MAYBE for extremely specialized applications like on a tight-clearance bridge or at an interchange.

Your better bet might be ex-NYC, which had extensive penetration into the Pa. Clearfield coal region and into West Virginia?

Conrail installed these in the 1980s.

Actual pictures of them here:

https://railroadsignals.us/signals/trilights/index.htm

Bingo!

I believe their use on former PRR territory started under PC, but they are all post-Pennsy iinstallations. PRR was ride or die on PLs until it died.

NYC was big on tri-light signals in their day. PC and CR changed all that.