History/Context: In 1947, the scientific instrument manufacturing firms of  Henry Hughes & Son Ltd, London, England, and  Kelvin Bottomley & Baird Ltd, Glasgow, Scotland, came together to form Kelvin & Hughes Ltd. Hughes Company History: Henry Hughes & Sons were founded in 1838 in London as a maker of chronographic and scientific instruments. The firm was incorporated as “Henry Hughes & Sons Ltd” in 1903. In 1923, the company produced its first recording echo sounder and in 1935 a controlling interest in the company was acquired by S Smith & Son Ltd resulting in the development and production of marine and aircraft instruments. Following the London office's destruction in the Blitz of 1941, a collaboration was entered into with Kelvin, Bottomley & Baird Ltd resulting in the establishing “Marine Instruments Ltd”. Following the formal amalgamation of Kelvin, Bottomley & Baird Ltd and Henry Hughes & Sons Ltd in 1947 to form Kelvin & Hughes Ltd. Marine Instruments Ltd then acted as regional agents in the UK for Kelvin & Hughes Ltd who were essentially now a part of Smith's Industries Ltd founded in 1944 and the successors of S. Smith & Son Ltd. Kelvin & Hughes Ltd went on to develop various marine radar and echo sounders supplying the Ministry of Transport, and later the Ministry of Defence. The firm was liquidated in 1966 but the name was continued as Kelvin Hughes, a division of the Smiths Group. In 2002, Kelvin Hughes continues to produce and develop marine instruments for commercial and military use. (See Note section this document for further information on the company's origins)This model parallel map ruler is a good example of the commercial diversity of navigational instruments made by Kelvin & Hughes after world war 2. It was made in numbers for use by shipping after the second world war and is not particularly rare or significant for its type. Also, it was made no earlier than 1947 as the firms of Kelvin, Bottomley & Baird Ltd and Henry Hughes & Sons Ltd who took over from Smith & Sons were not amalgamated until 1947. It can there for be assumed that this ruler was made during the company's transitional period to Kelvin & Hughes from Smith Industries Ltd.Metal parallel rule with Kelvin & Hughes Ltd, Made in Great Britain imprinted, numerous measurements, two handles and 3 hinges.flagstaff hill, warrnambool, shipwrecked-coast, flagstaff-hill, flagstaff-hill-maritime-museum, maritime-museum, shipwreck-coast, flagstaff-hill-maritime-village, parallel rule, kelbin & hughes ltd, metal parallel rule