The 1975 Decimo Vatman Memory. was very kindly donated by Barry Samuels

Specification:
6V (4 x AA).
8 digits, green fluorescent.
4 function, %, square root, memory.
83 mm x 130 mm x 28 mm (3.25" x 5.2" x 1.1").
Made in Japan.
The % key is marked "VAT" for use in calculations of Value Added Tax within the EEC (European Economic Community).

Thanks to www.vintagecalculators.com/ for the information