As I recall a Mill is a all caps typewriter used to copy messages and
radiograms by the Military.
On our Navy transport planes, we had such a device at the Radio Operators
position.

See URL:
http://www.telegraph-office.com/page...s_gallery.html


But Mill has historical reference -- see Henry Mill - URL:
http://inventors.about.com/gi/dynami...com/1714ad.htm

CL --- hunt and pecking