VINTAGE HP-21 Scientific RPN Calculator

Purchased at an estate sale. Therefore, we do not know the history of the unit. Bench tested to turn on and testing number keys only. No other testing performed. Please also note the following: -There is minor corrosion on the battery tab (see photos). -The battery tray appears to have been modified to accept standard AA batteries and includes battery springs. -The battery door does not close completely and may require tape to remain secure. -There are etched markings of a person's name on the front of the calculator (not shown in photos). Therefore, list as parts for the above reasons. AC adapter and batteries are not included.