I was the winning bidder on this item in the auction. There is not a lot of information on the Parkhurst vending machine markings. They are quite scarce and difficult to find on cover. The key thing about the Parkhurst vending machine is that it was the first, or one of four, machines adopted by the postal service to sell coil stamps to the general public. It was an experiment to see if stamps could be made available to the public and if the machines worked well or not. Here is a post card I found with Parkhurst vending machine markings. It was a new discovery at the time.