Terminated: unknown
It has all the basic functions, square roots, percentages, and even the constant π and a key for changing the sign of a number.
It has a hole at the top that looks like the socket for a power adapter, however there is no connector present. It does not look like this calculator has been tampered with so my guess is that TRANS EUROPEAN ELECTRONICS used the same case for multiple types of calculators.
Ome bug, according to this calculator, √-9 = -3.
This calculator was donated to the museum by Hugo van Leeuwen. Thank you, Hugo!