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

99xxx group.

These OBS were a perfect opportunity for vessels to use the

abbreviated cut numbers, and were very much appreciated by us shore

station operators.

73, Jeff KH6O

(formerly with NMO, USCG CommSta Honolulu)