The Atari CX-85
Sensing a need to add a more serious numeric setup for its Atari 800 computer
system, Atari introduced the Atari CX-85 numeric keypad which plugged into
one of the available front joystick ports on the Atari 800 and using a
special driver will allow the numeric keypad to be used with any Atari
program or for programming in BASIC or other programming languages.
The numeric keypad was also packaged into 2 packages: The Atari Bookkeeper
and The Atari Accountant.
Unfortunately Atari did not see the numeric keypad as a necessary part
of a standard keyboard and this product was not incorporated into the Atari
XL line of computers which would have given them a more serious and professional