This is the Hewlett-Packard 41cx or HP-41cx calculator.It is part of the HP 41 family which was introduced in 1979. There was the 41C, 41CV and the 41CX. The 41CX was introduced in 1983 and finally discontinued in 1990. It had numerous features including:
- Up to 6.4K RAM
- Up to 24K ROM built in
- 12 character high contrast alphanumeric LCD
- 4 expansion slots allowing additional RAM/ROM or external devices
- Reverse Polish Notation
- Key programmability
- Customisable keyboard
- Backwards compatibility with HP-67/97
- Over 30 ROM modules available
- A number of printer and mass storage options
- Optional bar code reader
An HP-41cx recently sold for $450.00 (7-03-2011). It was in mint condition and basically new in box.
A basic HP-41c calculator will sell for around $100. If it has peripherals such as a printer, cassette, or card reader then it can reach into the $200-300 range depending upon condition.