Alternate Mighty Mouse image buried in the driver?

Caius writes to tell us of how he found an alternate Mighty Mouse image in his System folder. While browsing its contents in iPhoto, he noticed two images that resembled the Mighty Mouse: One named "type1.gif," and another called "mouse5.gif." Noting that "Mouse5.gif" was the image used in the mouse's preference pane, Caius realized that "type1.gif" was slightly different. Specifically, it depicted a mouse with a clear shell (similar to the Apple Pro Mouse) and a "rubberized" central button. Could it represent an alternate design? If you have the Mighty Mouse driver installed, you can view the wayward image by typing the following into a terminal window (all one line, of course):

open /System//Library/PreferencePanes/Keyboard.prefPane/Contents/
Resources/type1.gif

Thanks, Caius!