Telegraph Talk and Talkers (1902)
books.google.com-a ) check out Leo Marks' "Between Silk and Cyanide", which touches on a telegrapher's signature 'fist' - they were distinguishing between different (German) senders of coded messages over the air.
-b) this is still relevant today for (especially amateur radio) morse code operators
LL commentary: https://languagelog.ldc.upenn.edu/nll/?p=67333
I think the anchors got trimmed off the URL, so this URL doesn't point to the correct page anymore. Page 227
Fixed now. Thanks!