If you are of a certain age with a predisposition to numbers, Hewlett Packard calculators are likely to conjure favourable memories.
The 12c for the actuaries, the 15c for engineers, the 41c for geeks who solved Rubik’s cube one handed behind their backs before breakfast.
In recent times, HP calculators deteriorated in quality to the point of unusability. The business outsourced manufacturing to China and the rest is history. Garbage came back with a bitter taste.
But, HP emulators are available from app stores. You can pay a tiny price and put a 41c on your phone, bypassing the horrendous lack of quality from Chinese hardware. It’s almost like old times.
Australian Actuary 
I still have my 12c – in perfect condition after 32 years. It’s one one my favourite possessions. I’ve often pondered how such quality results in no more revenue from that customer. They’ve made up for it on printer cartridges though. I’m a loyal customer of those!
The preface to the HP41c manual dated 1980 includes this:
“The success and prosperity of our company will be assured only if we offer our customers superior products that fill real needs and provide lasting value, and that are supported by a wide variety of useful services, both before and after sale.
Statement of Corporate Objectives Hewlett-Packard”
I’d suggest that people who bought HP products from those days became lifelong fans. So much so that Swiss company swissmicros.com makes HP clones that, I believe, have established an excellent reputation in a short time. The clones have benefited from imputed HP value of decades ago. Still, I can’t see see too many younger folk bothering with RPN, even though it is streets ahead of the alternative.