Based at the Truro Works in Truro Road, Wood Green, Guy's Calculating Machines Ltd was set up by Frank Guy. The company patented their first machine in February 1909.
The following explains how Guy's got a leg-up during the First World War:
We have now reached a stage in history when the world was enveloped in the turmoil of a world war. Apart from the destruction and trouble caused by such a time, it also brought problems in connection with calculating machines. One company, the B.P. and Anglo-Persian Oil Company, was unable to obtain the calculating machines it required, so they made an approach to Frank Guy, who since leaving the company of Charles Beveridge had been working as importer for Mercedes machines, but when the war started, trading with Germany ceased. The B.P. company gave financial backing to Guy, who made for them a copy of the Odhner machine in premises at Wood Green, in North London. This machine was called Britannic and was made primarily for the B.P. and Anglo-Persian Oil Company, but he was free to offer the surplus of his production on general sale.
From The Society of Engineers Journal 1969
By the 1920's Guy's was advertising the company as the makers of the only British calculating machine.
A copy of one of their machines is now on display in the Science Museum.
Frank Guy sold the company in about 1939. It moved to Witham, Essex, in 1965 and was sold by again in about 1969, by which time it had become a general precision sub-contracting works.