The station heard was almost certainly Cuban MCW numbers station M08a. They have a regular schedule on 5800 kHz at 0600 UTC.
Cut numbers are a shorthand method of using short CW letters in place of long CW numbers. In the case of M08a they use the letters ANDUWRIGMT to replace the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, 0. A=1, N=2, D=3, etc.
OK, you may notice I said this was M08a and they have a schedule on 5800 kHz, but you reported 5801 kHz. Neither of us are in error.
M08a most often uses MCW. This is a full DSB plus carrier AM transmission. They modulate a 1 kHz tone on the carrier. If you tune to 5800 in the AM mode you will hear CW with a 1 kHz tone. If you tune to this signal in the CW mode of your receiver, but tune to 5801 kHz (the center frequency of the CW characters) then you will hear the CW with whatever pitch offset your radio uses for CW, frequently between 600 and 800 Hz. By the same token you could tune 1 kHz below the carrier, at 5799 kHz, and hear the same signal.
M08a sometimes uses what look like a normal ICW (keyed CW, what most hobbyist refer to as “CW”) signal. When they do this they are most frequently 1 kHz under their scheduled freq. This is because they use the same 1 kHz audio tone as when they are in MCW, but the transmitter is in LSB mode, creating what looks like keyed CW 1 kHz under the scheduled freq. Very, very, occasionally they make a mistake and do the same thing in USB, resulting in keyed CW 1 kHz high.
Anyway, the next time you see or hear this station flip over to AM and see if the CW is still copyable. This will indicate they are in MCW/AM mode.
T!