I don't believe it is Swedish. Swedish carbines had an entirely different rear sight. The two pins (hammer and breech block) were held in with separate screws, often referred to as "moon screws". The Swede carbines were in 12mm. The rear sight looks large enough to be from a rifle. Has it been cut down? More photos would help.
It's on a net auction, have found special guns before because the seller didn't know what he had. Looks as a .50 caliber, and the big steps on the sight might be because of a heavy bullet???
The danish rifles / carbines doesn't have that big steps, and the reciever is not rounded like this one
Is the rear sight mounted backwards? Such sights in the US service usually (almost always?) face the other way. The clue is the sighting notch because its' sharp edge, or flat face, should be presented to the eye - for clarity/sharpness of vision - rather than the 'scalloped out' side of the notch.
Based on the limited information, I'm going to guess that it is an Egyptian contract. The muzzle end of the barrel is worn considerably, an indication of a harsh environment and a characteristic shared by a large number of Egyptian Rolling Blocks. The hammer and breech block spurs are also very worn on the ends; checkering is very light. The butt stock has a sling swivel so possibly it was an Egyptian rebuild where they also put a rifle rear sight on a carbine. There is no graffiti or stock carvings as is typical on Central/South American Rolling blocks. I'm going with an Egyptian contract that has been modified over the years.