The HP-35s is a programmable scientific calculator from Hewlett-Packard. It was introduced in 2007 for the 35th anniversary of the HP-35.
I personally wanted to get one because it is the only programmable calculator allowed on the Fundamentals of Engineering exam and because it uses Reverse Polish Notation.
This is one of my endgame calculators and took me some time to find at a fair price. They aren’t super rare, but they often sell for $300+ and that was way more than I was willing to pay. Fortunately I was able to find one for significantly less and that's the model I have today.
