Terminated: 1980
It is an RPN scientific calculator with trigonometric functions in DEGrees, RADians and GRaDients. It can also do a series of English/metric conversions.
For more information on this beauty please refer to the better sources, like The Museum of HP Calculators (link valid 2024-04-28).
Many thanks to Richard Pilkington of the University of Salford for donating this calculator to the museum.