Jerom (96338) writes "The HP 15c, back by popular demand!
HP reintroduced the HP 15c Scientific Calculator, first launched in 1982. The 15c is one the most advanced scientific calculators in the HP line-up and an essential tool for scientists and engineers. Also featuring RPN entry, the 15c is programmable and offers built in support for complex numbers, matrix math, numeric integration and root solving.
Discontinued in 1989, the HP 15c has lived on as a mobile app. For a limited time, HP is making the 15c available with its same intelligent design, but with 100 times faster processing speed than the original.
More information about the rich history of the HP 12c and 15c calculators is available at www.thenextbench.com."
Link to Original Source