Give cutemouse a try?

Cutemouse does not work. I have tried Genius, Logitech, Microsoft drivers as well.
This mouse was also sold for the MAC G3, so maybe a specially wired gender-changer is needed on the PC...? I only have simple pin-to-pin gender changers. Pls. look at the attached photos.

are you sure that's not a ps2 mouse with a custom DB9 connector (going to some custom port...?)
I see 4 pins and 4 pins is all PS2 protocol needs...

I really have no idea. Of course, I can dissect this mouse further and electrocute it 😀 You think I should cut off the tail of a dead PS2 mouse and also cut off this connector then transplant the proper PS2 tail to the YT1? But first I should know the pinout. The donor PS2 connector end is standard, isn't it? So I only need to find out the pinout on the YT1.

The full part number of the microcontroller could help. Maybe it's an USB mouse.

Bullseye! Thanks, h-a-l-9000.
It is indeed a USB chip - CY7C63743-PC. So, for me, it is absolutely useless in DOS.

It's not just USB, it's one of those multi-protocol chips that also supports PS/2. So if you can figure out how to wire it up, it should work just fine on a PS/2 port.

OTOH, unless there's something particularly special about that mouse, it probably wouldn't be worth the time and effort to hack a new connector on it... regular PS/2 mice are common and cheap.

You are right, it is not worth the effort. Now that we know what this mouse really is...