Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
I have a CB500 K3 and was a German import checkout the parts book from deltarider page 4 frame and engine numbers 500k3's have frame no's starting 1000 your frame must be a 550 k3.
It looks like Honda had still some 500 engines on the shelf and/or that these Scandinavian countries had legislation (think: drivers license and/or insurance) that drew a line between 500cc and motors over 500cc.Maybe the CB500K2 (ED, F, G) marketed on the European continent in 1976 was a similar story, as this model shared many things with the CB550K2 that was marketed in the US the same year.