I think there was only one ceramic company in Egersund, it's not a very big place
http://en.wikipedia.org/wiki/Egersund The factory closed down in 1979 (burnt down?) and there is lots of information here
http://museumsnett.no/dalmus/, click on Egersunds Fayancemuseum in the left hand menu, in Norwegian unfortunately but there are some piccies.
I found a part set of this fifties/sixties stuff last week