Captain King's pocket watch contains photographic images of his parents (~12:00) which must predate their stated 1833 date of death. The earliest known photograph of a person by Daguerre is from 1838 and were all exposed onto metallic silver plates.
The soldiers of the Khyber Rifles are Afridis. However, the knives which they draw are kukris, the traditional knife of the Gurkhas. Afridis would use a pesh-kabz or Afghan Knife which has a different shape.
Captain King is shown wearing the rank markings of a Lt Colonel (crown and pip). Additionally, the 'Scots' pipers are all playing Irish war pipes (two drone - Scots pipes have three)
During the avalanche scene, toppling trees are clearly rootless.
When Captain King salutes Susan, he gives the American salute of palm facing down, when in the British army, the palm faces forward.
Though it has already been mentioned that Capt. King is wearing the rank insignia of a Lt. Colonel, so is the General (Crown and Pip), while all the Lieutenants are wearing Crown insignia, which denotes the rank of a Major.