It also says that the stylus is "Wacom Serial
Tablet PC Stylus".
[...]
Under Tablet Types: Serial Tablets, it says:
Note that as of version 1.0, the xf86-input-wacom driver no longer
supports serial devices.
Debian testing has xserver-xorg-input-wacom version 1.2.3-1, so there's
a good chance that 1.0 is already considered "old". 🙁
I couldn't find any indication of someone else having picked up the
development/maintenance of the support for serial wacom tablets.
If you're motivated, the old code is out there so it shouldn't be
impossible to resurrect it.
Stefan