I made a purchase mistake this weekend. I relied on the seller's description and I didn't look closely at the picture. Also, the item looked smaller in the picture than it is. This gage was described as a trolley/streetcar air gage. The lens bevel is 6 inches across, so it's a little bigger than the duplex gages I am used to seeing. The black needle is marked train line and the red is reservoir and they have separate "fields". The black needle sweeps down and the red needle sweeps up. It is marked General Electric, but would it have been off of a railroad car or possibly an interurban? The seller bought this at a church rumble sale in Midlothian, Texas about 15 years ago and knows nothing else about it. The Fort Worth interurban ran motor/trailer combinations on the express train, but I don't know if this would have been on the trailer or the motor if at all. I see no markings on the outside other than the face of the dial and the markings on the nipples that say "brake-cyl." and "reservoir".
Bonus picture of the rest of the stuff on my desk. Most of this is destined to be used in our NTT No. 560 project.
Thanks,
Andy