All are views of Addiator serial no M076362 which is a Sterling model dating, I think, from the 1930s. It measures 7.1" x 4.8" and has a black leatherette case in which it can be flipped over for subtraction. Like all the big, early genuine Addiators it has the addition and subtraction slides on opposite faces. It weighs approximately one pound so it was a heavy item to carry around in a pocket.

 

Best regards

 

David