Postal Letter Sorter

My maternal grandfather, William Lee "Johnny Bill" Wright (1919-1973) worked for the post office.  My mom took these pictures at the Pony Express Museum because they reminded her of a story about her dad:

I took these pictures at the Pony Express Museum because they reminded me of the clerk letter sorter that my dad had to use.  It was about half this size.  He had a long box of cards and he would practice sorting the cards into the pigeon holes.  He had to take a test yearly to see how fast he could sort the mail and not make a mistake.  I think he was given about 100 letters and could only miss less than 5? in about a minute.  I thought you would like this information.

Mom