This is an old Hewlett-Packard programmable scientific calculator. It features Reverse Polish Notation (RPN) operation and binary/octal/hexadecimal conversion functions for programmers. It runs on three button cell batteries (LR44). The case of this item has been cleaned, and it has been confirmed that it performs basic calculations correctly, operates without issues, and passes the self-test with no display problems. However, the functionality of all features has not been verified. Please examine the photos carefully to assess the condition of the main unit, as it has minor scratches and stains. A dedicated pouch is included with the main unit. It is currently working, but due to its age, the operation after shipping cannot be guaranteed. Please feel free to comment with any questions before purchasing.