I think what you need is info about Ronning's Knife Company. Minneapolis. I live in the area, but have never heard of them. What you may have is a knife made in Sweden as a private label for Ronning's. A photo might help somebody here to identify it.
Or, you could try outdoorfishinggear.net, which has a list of about 1100 filet knives for sale. If you leaf through all the listings, you may find a picture of a similar knife made for Ronning's.