The communications typewriter, known to Radiomen as a
"mill" has special features to facilitate the work of Radiomen
and other communications personnel.
In plain language, context would help distinguish between
similar characters such as 0 and O. The mill has a
slashed zero to differentiate zero from capital O,
because most traffic was enciphered and letters and numerals
were mixed together in groups. The mill also has a 1
key, whereas on other typewriters of the era, you typed a
small l to represent the numeral 1. The 1 key eliminated
the necessity of using the shift key to make a 1. The
punctuation symbols correspond to different numerals on the
mill because of the numeral 1 taking the normal location of
the numeral 2.