I love the postal history.
Then looking at these, it suddenly occurred to me.....doh!
Sitting here in my studio is a piece of railway postal history and I forgot all about it.
I've had this small (compared to the above pictures) 'mail slot' for years. I use it now to hold magazines and material for freelance jobs.


It's inscribed CNR in ink on the upper corner, and some of the pigeon holes still have typewriter written labels on them.
Right under my nose.