The pocket sized 1678 arithmetical machine. (Click on image to enlarge).
A precursor to the computer, one of the earliest surviving pocket calculators, comes up at Christie’s bi-annual sale of Travel, Science and Natural History in South Kensington, London on October 10. Made around 1678 by watchmaker Rene Grillet de Roven it is one of the earliest mechanical calculating devices known to exist and the first portable device. Only three other known examples of this design survive. It is estimated to make £70,000-100,000.