Here’s a little snippet from the Ham Radio History Yahoo Group about the origination of cut numbers.
“Cut numbers” were used extensively on the maritime CW bands:
Every ship at sea sent its weather observations (“OBS”) every six
hours (0000Z, 0600Z, 1200Z, 1800Z) to what ever shore station it was
in contact with. These WX OBS were encoded into 5-digit number groups,
always beginning with 99xxx.
After I had a dozen or so vessels lined up and QRV to work one at a
time, I’d only have to send AA NN, and the ship at the head of the
line would burst forth with their number groups, beginning with the
These OBS were a perfect opportunity for vessels to use the
abbreviated cut numbers, and were very much appreciated by us shore
73, Jeff KH6O
(formerly with NMO, USCG CommSta Honolulu)