Since we're limiting this to things on my desk I can't do any more deep cuts out of my calculator collection, but this one is still somewhat interesting.

The HP 32S was my friend throughout university, it replaced the 15c I used before which does not live on my desk. The notable thing about the 32s is the fact it's an RPN calculator. RPN calculators are the best way to have friends never ask to borrow your calculator. The exchange will start by them asking to use it, you saying sure, and them handing it back a few minutes later without saying a word.

There's two kinds of people in this world. People who go "wtf" in an interview when asked to create a calculator program using a stack, and people who were oddballs and for whatever reason used reverse polish notation devices.

For those not familiar, rather than entering values into the calculator in "10+10" fashion, you instead provide it a compositional set of values until an operation is provided (10,10,+) at which point it executes. The why is, this type of operation allows the calculator to more naturally process operations, and eliminates the need for parenthesis which makes the operations less error prone in practice and easier to track.

The 32s had a 4 year run before being replaced by the 32SII. In the same way using a Curta will give you a significant understanding of how radix computations and floating points work. Using an HP 32s (or any of its predecessors) will do the same for algebraic functions, because you had to program them yourself using a basic label address system that also had subroutine support.

Kids who grew up with graphing calculators don't know how good you had it 😋