Here is a Swedish rifle, model 1815/26 or 1815/38, according to what I could find online.
https://www.passionmilitaria.com/t206783-fusil-silex-reglementaire-suedois
https://www.horsesoldier.com/products/firearms/longarms/38599
https://www.warrelics.eu/forum/world-firearms/swedish-flintlock-rifle-793123/
The second reference specifies that the lock is equipped with a "Dog Lock," a type of safety that locks the hammer in the half-cocked position.
NT refers to the Noortälje factory. The letters CAV, PW, crowned NT (perhaps a small hallmark of the Noortälje factory?), and BG inside the drum spring remain mysterious.
GP with the help of HPH.
