follow a link in another thread I found another Geco/Kaba for sale in Norway thats very close to your rifle
http://www.beverensport.no/products/gustav-genschow-co-modell-98

serial number: 986
again a rifle in 10,75x68 that was probably rechambered in the past! the cross bolt was set when the rifle was rechambered but have no clue about the little screw in the stock over the trigger. maybe another little cross bolt?
the number is close to rolf's rifle and whats visible on the small pics having the same fore and rear sights. its only a fixes rear sight without the folding leaf rear sight we see on the later rifles. the design of the front sight is also very different.
the stock and especially the trigger guard looking like we know from rifle's with higher serial number.

the older and newly front sight:

the older and newly rear sight:

a quick look at the iron sights makes it easy to distinguish the two versions from each other