Tinker:
Here is the listing for Jeffery's Patent aperture sight in their 1910-11 catalogue:

Check the last line in the ad: "Jeffery's Mannlichers at 12 guineas are fitted with these sights without extra charge".

Note that there are already a couple of pics of this type of sight on NE.com, in the .416 Rigby thread on the Mauser Photos forum. Jump to it here and scroll down to the second set of photos, in MFC's post.