Hi I recently acquired a Marlin 336 with serial number first two digits of 26; I determined this indicates it is a 1974 vintage rifle. The barrel measures 16 & 1/4 inches, straight stock; the model is only 336 (no alpha characters after the 336). Has a ramp front sight. From the research I've done, I can't determine if this gun is an authentic, stock length barrel from Marlin or if the barrel has been shortened, which would mean this gun is not authentic. Attached are pictures of the firearm. Any help would be appreciated to help identified if this is an un-modified, original firearm or if the barrel has been altered.