PRR Drinking Glasses

I got these lovely PRR drinking glasses at a flea market. The dealer said that he had cleaned out the estate of an old railroader. These are a boxed set (no markings on the box) and each glass features a different Northeast Corridor city. I have never seen another set like this, no one else seems to have ever seen them either. Were they a shippers premium? A gift for station agents? No one seems to know. What I do know is that they are great glasses (I use them) and they are great when I entertain guests. Just match up the city to the guest. You can't get their glasses mixed up for refills!