C40 yachts were made in Northern Sweden by Umebåtar, from the mid-1970s until the early 1980s.
There isn´t very much information about these boats on the internet. There is a link to a Swedish site where you can find the basic facts: www.sailguide.com/ (click on "båtfakta" on the left and you will get to a page where you can choose from an alphabetic register. Hopefully you can find your way even if it is in Swedish.)