Last night around 0600UTC I heard an odd CW signal on 6937 from my
Southern California location. The signal was weak and about 25wpm,
a little faster than I can easily copy. It appeared to be a beacon
sending a string of mostly numbers. (Uncut.) There would be about
a minute pause between each transmission of several dozen characters.

Each string would begin with the Morse code "dash" character _..._ and
would end with five question marks. (?????) Most of the text were
numbers with the occasional "T". The spacing of each character was even,
not the typical five-figure number groups.

Any idea what/who I heard?

Outside of the ham bands, I rarely hear any CW on shortwave these days,
except for the "cut" tone-modulated AM CW on 5800 from Cuba.

Thanks in advance.