Hello Dotty, Sigma is a Spanish make.
http://www.es.wikipedia.org/wiki/Elgóibar will take you to the Spanish Wikipedia page, and you can hit the translate button. Halfway down the page in the section about the economy of the town you will find mention of Sigma being founded by Estarta and Ecenarro.
harrishs has a lovely Sigma treadle which she posted on a thread in July.