At this month's SCCAN and FCUG meetings, it was verified that the package I received did contain a 1350 mouse. Predecessor to the 1351 proportional mouse, the 1350 was more like a joystick with two control buttons. I will try to post pictures of the box and instructions later on, but enjoy some of the quotes from the packaging.
"When your Commodore 128 is used with a 1350 Mouse and Mouse compatible software, that's all it takes to create pictures and quickly edit documents."
"The result is an increase in the ease of using your Commodore 128 and a reduction in the use of complicated computer commands."
"The Commodore 1350 Mouse connects to the joystick port on your Commodore 128 and requires that you use Mouse compatible software."
OMG, the marketing! It operates just like a joystick... almost any game (or 'professional' software that allows a joystick) will work just fine with the C1350. It has nothing to do with C64/C128 compatibility!
Humor aside, it is disappointing there was no utilities disk included.