The "vanilla" mouse is the earliest of the three Mark II mice pictured on oldmouse.com, judging by its lower serial number 07305. The insulation on its very thin black cord has cracked off where the cord exits the mouse, revealing tiny rainbow colored wires. Otherwise, the mouse shows no external wear. But, the large ball makes a faint grinding noise when rolled. There is no way to get inside the ball housing to clean it.
The case top is an off-white plastic, barely darkened from the faintly green tinged white interior. Its three black buttons make a nice clicking action. They are so close on this 3-¼" X 2-1/8" box that they must have been a bit of a challenge to use over long periods.