I've heard on several occasions a very strong (S9 to 20dB over S9 in
mid-atlantic US) CW transmission on 10125 kHz with 5-letter groups,
separated by BT's and AR's. Speed is probably 10 or 15 WPM. Hours are
sporadic but it happens most often the middle of the night (like 0500
through 1000 GMT).

Is this some sort of scheduled code practice transmission, or is this a
variation on the "numbers stations" coded messages?

Tim KA0BTD