I bought my 1931 Mail Truck in 1957 just three years after it was retired from the Gloucester, Massachusetts post office. It was their only mail truck so it was sold by bid for it alone. A local garden center used it for 3 years before my purchase. It was a running and drivable truck and for over 50 years I used it regularly for Model A club activities, including tours and for flea market vending. I was a member of the Postal Chapter and my truck was used by the late Aldie Johnson for data in his mail truck hard cover book. Time passes and it was finally restored and a few years later I sold it to a gentleman who had several unrestored mail trucks. I had it about 56 or so years, and one of its interesting duties was to bring Santa to the town Christmas Tree every year with presents for the children. Before it was restored it was lettered U.S. Mule as my local Postmaster advised me not to use the word Mail.
One last word is that I was told all Model A mail trucks that were in use in any town or city were replaced at one time, under a bidding process. A city might have many and the successful bidder was often a junk yard. One junk yard I visited a few times had a bout 15 retired mail trucks side by side and each was full of parts the yard wanted to keep dry. That was Bill's in Valley Falls, Rhode Island many years ago.