The ADB mouse. ADB Mouse II would be too late.
Model G5431/A9M0331 seems to be frequently listed for it.
Interestingly, the wrong mouse is on the Wikipedia picture with the Classic.
Also, it should be the 'light ball' style ADB mouse.
That's one reason that I asked. I had a fair bit of Apple kit, back in the day and was sure the ADB Mouse II was later, but didn't completely trust my memory.
What does "light ball" mean?