One of the Y's has a piece cut out of the block at one side. This won't effect the printing of the letter. It seems like sacrilege to us but printers/compositors sometimes used to do this to get the letters to fit together better when they were setting the type.
There is an O carved on the reverse of the Z - again something that was done if the type setter needed an extra letter. It all adds to the history of these old block alphabets.