I have a KF 940 also. I bought it new in 1972. It was imported and inspected by the CF Martin Co. It still has the label inside.
The rosewood back is pretty unique. The back also has a large wedge of a very light wood. I don't know what it is but it's done pretty well. Probably why I was willing to pay so much.

There are 5 kinds of wood just in the body of this thing.

But... I can't find out anything about this model that I don't already know. I was starting to think I had the only one. I like it. It plays easy and sounds great. I have no idea what it's worth. I probably got clipped but it was new and in a store and I was very young. I think I paid about $400. for it. Still doesn't have a scratch on it.