The Pitagir, an Italian old calculator made of paper for children in 1940s 

This one is the Pitagir, a simple calculator made of paper, used in the 1940s years in the Italian schools.
It was used by the children in the elementary schools.
And actually this is a multiplication table, with also the basic formulas for geometrical shapes.
Very easy to use and to transport.
If you lke vintage calculator or vintage devices, could be interesting.