Thanks for the photo!

About dating that sporran, it would help to see the back of it, as the rear of horsehair sporrans has changed more over the years than the front.

In the book Scottish Regiments and Uniforms by A H Bowling there is a photo captioned:

Men of the 3rd (Militia) Battalion, Cameron Highlanders, in Foreign Service Uniform for the South African campaign, 1900.

These men are wearing sporrans which look very much like yours.

So until I find out more, that's my guess: 3rd Batt Cameron Highlanders 1900.

The use of white rope to suspend the tassels hints at an early period- by the 20th century chain was normally used.