Microsoft issued its unofficially-called "Dove bar" mouse, first released in 1987, as a transparent mouse officially labeled Serial-PS/2 Compatible mouse. Rather than crystal clear, it's grey tinted transparent. One eBay seller claimed Microsoft produced only 150,000 of the clear mouses. This special edition probably marked Microsoft Mouse sales reaching a million units in 1988. Or maybe it celebrated their award in 1989 of a patent for internal mouse technology.
The body shape of this mouse remains constant but its functioning evolved to protocols able to switch between bus, serial and PS/2 ports.
The label reads:
Serial-PS/2 Compatible Mouse FCC ID: C3K5K5COMB Part No. 28898 Microsoft Corporation Made in USA Patent Nos. D302,426 & 4,866,602 Serial No. 3885712