Back in the mid 80s, Atari was sticking their hands in lots of pies. Not only were they selling the XE 8-bit computers and the new ST computers, but they also dipped their toes in calculators for a while. Perhaps Jack Tramiel was nostalgic for when Commodore sold calculators in its early days.
Atari actually made quite a few different calculators and I recently picked up the CC1010 solar calculator1: