That's the serial mouse I used to
use with my first IBM AT when I 
started to work for my current employer
back in 1987.

It is the original MS Mouse design
with a 25-pin "fullsize" serial connector

Plain white case with
unstructured surfaces

Molded 9-pin female Sub-D connector

An adapter from 9-pin to PS/2 
round Mini-DIN-6
came with the mouse

Serial-PS/2 Compatible
Part No. 28898
=5V 20mA

The original "trapezoid" style.

This was the mouse introduced with
the PS/2 machines back in 1987.

"Model 6450350, P/N 90X6778"

Two medium-grey buttons,
"IBM" engraved at the top front

Cable with a slim connector

There are however variants existing.

Left side the US / Ireland made mouse:

Retainer with arrow pointing towards front,
Large, grey mouse ball.


Right side the Taiwan-version:

Two arrows on the retainer showing the 
unlock direction,
Smaller and lighter black mouse ball.

This mouse -in addition- has the plug with
the bigger outer case as it came for the
PS/Value Point Series.

This mouse came along with the 
PS/Value Point Series 2.

Has two buttons entirely covering the
upper edge and case entirely in ivory.

"Made in China" with a simple, thin PS/2
plug with only an arrow as marker for
the "up" position.

This mouse came along with the 
PS/Value Point Series 2 and the last
Series of PS/2 machines.

Has two buttons entirely covering the
upper edge. Upper case is ivory, lower
part of the case is light grey.

"Made in Ireland" with a big PS/2 plug
molded with "IBM" as marker for
the "up" position.

Differences in coloring

Underside Layout differences

This mouse came along with the 
PS/Value Point Series 2.

Like the "Fat" mouses but has dark gray
buttons and case entirely in ivory.

"Made in Ireland" with a thicker PS/2
plug with "IBM" molded into it.

Manufacturer Model: M-S34
ASM P/N 76H5078
FRU P/N 76H5080

Made in China

"Made for IBM by Logitech"

Gray cable with green PS/2-plug and 
"mouse" symbol molded into.

Plain white - not even an IBM-logo.

Intended for use with Netfinity and
the black series of Intellistations
resp. the Netstations.

Manufacturer Model: M-S34
Model   12J3615
ASM P/N 12J3616
FRU P/N 12J3617

Made in China

"Made for IBM by Logitech"

Black cable with green PS/2-plug and 
"mouse" symbol molded into.

Netfinity-black - with blue IBM-logo.

Size (L x W x H): 41 x 20 x 13 cm

Made by Tamiya, powered by electric motor
and a 10 Volt NiCd racing battery pack.
Mechanical speed controller - has only
two speeds practically in either direction.

Using this thing in the backyard in case
I am frustrated or clueless and simply need
a break from all the computer and Internet
hassle.

Car is pretty fast ... hard to control.
Has various "in-fight marks" already on the
Lexan body.