That is the Crown / Husqvarna mark on the barrel . Serial number will be on the tang under the wood & maybe on the bottom of the barrel . The straight rifling is for a 20 gauge ball type ammo , but also for 20 gauge shotgun shells . I think 2 1/2" shells ???????????? A twist in the rifling would throw shot in a circle like a donut , so it was made straight for multiple 20 gauge use . Looks like a birch buttstock ? The guys on the Swedish Civilian Firearms Forum will probably know the model . I will move it for you .

 

I'd guess it's a Husqvarna model 12 or 13. Remington rolling block action . According to the guide, straight rifling was an added option for use with ball or shot. I've heard these were typically used for hunting capercaillie. Ive always wanted one, but could never find one with the right price in the right arrangement. I bet they're quiet with those long tubes.

 

What length barrel does it have ? 100 cm ( 1 meter ) ?

 

I have a HVA #12 shotgun with 16 gauge smooth bore ( shiny bright ) . Walnut checkered stock with cheek rest . All matching serial #50305 . 95 cm barrel length .

 

Swede, that's a beauty and it has the safety hammer...that's the kind to buy right there.