OMRON 8SM Calculator with Retro Blue Protective Case

1970’s Vintage OMRON 8SM calculator, working with case. Condition is used, this is a vintage item. Made in Japan and has original owner’s name written on the back. As with everything these days battery's are not included, I do not know what that connection on the top is for, sorry but I have included a photograph so you know what it looks like. I would suspect a power source but again I am not completely sure. Measures 7.4 × 11.7 × 2.4 cm.