Imperial 81SR

Display is 8 digits, green fluorescent in a single tube.

Scientific.

4.5 v (3 x AAA).

65 x 95 x 23 mm (2.5 x 3.75 x 0.9").

Made in Japan.
Imperial Typewriter and Business Machines Ltd.

A very tiny scientific calculator only just bigger than a credit card, though much thicker, however of limited capability.

Imperial models