This calculator comes from the 80's but in some circles is still considered to be a premium financial calculator. Full documentation is still available online but I still have the Solutions Handbook that came with it (see photos).
My dad, a statistics geek, used it extensively in his work and raved about it's "reverse Polish notation".
The only thing I know about reverse polish notation is it is an advance calculator methodology and is a time efficient way to run up some numbers.
If your loved one knows what reverse Polish notation is this h-p 12C may make a great seasonal gift.
In person cash sale at the Boone Mall preferred or a bank wire transfer if you are not a local.