The Mouse Systems optical mouse requires a metal reflective "desk pad" with a grid of blue ink for the "warp," so to speak, and infrared ink for the "woof" over a mirrored surface. Earlier Mouse Systems pads' coarse grid consists of about two dozen blue lines per inch on a silver ground. The M-4 uses a mesh several times finer of hair-width blue lines on the silver pad. Two rubber-like strips on the back anchor the pads.
Professionals used the 9" x 11" size. Less graphic intensive desktops were served by the smaller 7-3/4" x 9" size.
M-1 - The branded pad with a coarse grid used with the VisiOn M-1 Mouse is numbered is 400207-176 REV 5.
M-2 - The next model came with a similar pad. The coarse gridded pad that came with the M-2 Mouse is numbered 400207-003-REV. 3.
M-3 - Presumably this mouse continued to use the original grid pattern.
The M-4 came with a 7-3/4" x 9" fine grid pad. One numbered NCV 402105-003 came with Sun M-4 mouse.
The mouse uses a two sensor LED design, one for each direction, to determine location and speed of the cursor. The grid pad is essential. On-screen cursor movement is erratic if the special mouse pad is not oriented properly in relation to the mouse. From the M-1 Manual: "Mice are normally shipped so the pad is horizontal." DIP switches, however, allowed customization: "The pad orientation can be adjusted to suit your desk space or screen aspect ratio preferences. The mouse is roughly rotation insensitive to ±90º from nominal (straight up and down)."
Here's how to customize the rotation: "The mouse must be opened to change the DIP switch settings. Remove the two screws on the bottom of the mouse. Then place the mouse on a table as if you were going to use it. Then remove the top of the mouse."
"There are only four things inside the mouse; 2 lenses, a PC board, and a rubber light shield. Please note the placement of these components when you open the mouse. DO NOT touch the mirror; it is easily scratched. DO NOT touch the LRDs; they have been bent in that funny position in order to provide the proper amount of illumination. When assembling the mouse, be sure the rubber light shield is centered (sec the dot on the plastic case)."
Illustration of how to hold the mouse from Designer Pop-Up Menus User's Guide by Mouse Systems 1984.