Secondhand HP50G calculator, hardly used except in a few tests.
Works well for complex numbering in matrix formulas . Includes control graphing of bode plots,nyquist,nichols and root locus.
Nice for stats, includes all the distribution functions etc...
You can store and view text files...
And of course does all the standard stuff including the plotting of polynomials..
I have the manual,pouch and driver cd etc...
Extract from HP website:
The ultimate graphing calculator for surveying, engineering, math and science professionals and students is even better. The new HP 50g graphing calculator features an SD card slot with formatting functions, RPN~, Algebraic and Textbook data entry, the largest high-contrast screen with more usable space than ever, serial port and USB and connectivity. Plus, HP Solve, structured programming and Computer Algebra System (CAS). You also get the reassurance of award-winning HP support 24-hours a day.

Features |
 |
 |
• | Massive 2.5MB total memory—512KB RAM plus 2MB flash ROM for performing future upgrades |
• | Equation library and 2300+ built-in functions—ideal for both professionals and students |
• | Choose RPN, Textbook and Algebraic entry and customize data with four font sizes and styles |
• | Enhanced HP keypad with re-definable keyboard and menu keys allows for reduced keying errors |
• | HP Solve application allows you to type and store an equation then use to solve any variable |
• | Easily perform complex arithmetic and calculus functions with advanced Computer Algebra System (CAS) |
• | New powerful SD card slot allows you to format your card right in the calculator and expand memory |
• | Calculate advanced expressions and view solutions in 2- or 3-D graphical representation |