We're having flashbacks. They even got the sheen on the keys.
The i41CX+ RPN calculator looks and functions just like the graphing calculators that are standard in high school classrooms today, such as the TI-83+ or HP-41C. The interface captures the nostalgia of learning to use a scientific calculator, but only after you take some time to figure out how this app actually works
This graphing
calculator app is suitable for scientific, financial, mathematical, and
engineering applications. It supports 319 slots of main memory for data
storage and boasts 200 built-in functions, 600 extended memory slots,
and over a dozen pre-installed applications, with the ability to add on
more. It's also considerably cheaper than investing in an actual
scientific calculator, once you own an iPhone or iPod touch.
The i41CX+ also supports printing, with the ability to take a
snap shot of your graph, which you can then email to yourself and print
out from your main computer.
Instead of lines, every coordinate has its own point, which
makes figuring out the coordinates and plugging them into an equation a
cinch. You can also adjust the calculator’s graphing speed or use the
iPhone keyboard if the old school keys start to feel archaic.
Does everything you need for analytical mathematics. Can be used in professional fields. 
Lack of documentation makes the calculator difficult for number newbies. 
