This is the installation and operation manual for Racal-Vadic VA3450PSG-Series Modems.
It isn’t exactly Apple II-specific, but my first modem was the ‘S’ model. It worked with the Apple /// my father got from his job, and it worked even better on my Apple IIe with ASCII Express Pro. I think Racal was a much more popular brand in Europe, as no other Apple II user I knew had one. All my friends had Hayes or, if they were rich, decked-out Novation Apple Cats.
Though the manual lists all of these modems as 300/1200, I specifically remember that when we got it, ours couldn’t do 1200 baud until years later when we bought a ROM upgrade for it.