Mechanical Calculators:

A long time before modern electronical calculators there were many different mechanical ones. Some of them are well known as the abacus or the slide rule which we all used at school. So let me just give you a short overview on some very special calculators:

Model I Feature Model II
8 x 6 x 11 Keyboard 11 x 8 x 15
8 columns Result Dial 11 columns
11 places Add / Multiply to 15 places
6 places Divide to 8 places
53 mm Diameter 65 mm
85 mm Height 90 mm
230 g Weight 360 g
Both models were mathematically identical, the only difference was the number of colums and places. If you want to try a Flash6 emulator of a Curta, try this.

Circular slide rule:
There were many different manufactories that produced this type of slide rule. The great advantage of them: They were small and looked much more nicer.

Circular slide tubes:
You will find two manufactories that produced different slide tubes. This one is from Loga, made in Switzerland.