John Rigby & Sons No. 1 Mk.III Sniper

[Promo]

Boy, I'm a bit stupid ... why didn't I check the drawings for the inside dimensions of the scope?

Clearly, the front scope ring is shown with inside diameter of 0.982" while the rear scope ring having a radius of 0.491" (so also exactly a diameter of 0.982").

Having re-checked my rifle a few times and trying to fit a 25mm scope which is clearly not held in place I can confirm my rifle would need a 1" scope tube. This therefore leaves two possiblities:
a) the rifle was manufactured for a Fuess/PPCo type scope with 1" tube
b) it was modified at a later point of time to accept 1" tubes

I don't think that possibility b would apply, because it would also mean there need to be additional milling marks visible at the rear scope ring, what clearly isn't the case. Additionally the left rear sight protector is milled off, so definitely a scope with capstans for lateral adjustment. Anyone had seen a scope which would fit this description?

PS: an interesting detail, the original drawing dates to 01.12.1914. Per the book of Skennerton Rigby received a contract to supply and fit telescopic sights on 13.01.1915 for a total of 21 rifles (less than a month later). It is now my personal assumption they ordered 21 to keep one for the Pattern Room, what do you think?
Skennerton also lists an additional contract for Rigby dating 02.03.1915 for 100 rifles. So there could originally had been up to 121 of these rifles being made.

Edit: Rob, same dimension both at front and rear of front scope ring, sorry it took so long to let you know!