I am curious and the information is either nonexistant or speculative at best. The Ti-30 (not the newer morphed calc variations) was the most sold ever calculator for its time and may be the most sold calc ever, but then again maybe not. No calc compared or ever has for its two to three year reign as the most popular, most sold calc of all time (only because they were cheap, and actually I had to buy two (helping Ti's #'s), since the keyboard wore out quickly, then after a worn out ti-55, I switch to a quality hp).
However, the Hp12c has been on the market for nearly 20 years. Perhaps it can lay claim to being the most sold calc in calculating history of sales?
Opinions or facts, anyone? Just a curious question.