The diplomatic ciphers used thousands of characters. Even a single cipher sometimes used a couple of hundred characters, so they got their ideas wherever they could find them.
They used letters, numbers, Latin, Greek, math symbols, astrological symbols, kabbalistic symbols, and many invented shapes.
I have marked the ones that are specifically borrowed from Latin scribal conventions:
They used letters, numbers, Latin, Greek, math symbols, astrological symbols, kabbalistic symbols, and many invented shapes.
I have marked the ones that are specifically borrowed from Latin scribal conventions:

