Without too much investigation, this came up:
https://ia902703.us.archive.org/10/items/Fm24-6/Fm24-6.pdfIts a War Department Radio Operators Manual.
In this, some of the prosigns are explained. It really does look like morse code to me. And some parts look like standard radio procedure.
For example 'AB' meaning All Before, rather like a message ending.
'M' meaning start of message
'V' for a sent from callsign.
'D' could be meaning Deferred and there's a small chance thats the reason the following line was crossed out because it was not important enough?.
'P' would be priority and
'O' would mean Urgent!
Not all the characters are explained but some do fit the pattern. The actual 'payload' or message to convey though is a mystery. This could be absolutely anything if this was indexed in a secret code book. Anything from 'i would like a cup of tea' to 'drop the bombs now'...
Edit: also see the 'x' exactly above the 'O' (urgent) character.. coincidence? or maybe a marker for it.