Perhaps there's here some misinterpretation.
That rifle isn't a Rigby clone or some Rigby copy; it's merely a "Dorleac & Dorleac" rifle, a new creation mostly inspired by the light, simple, stalking rifles produced before WW1 by the great English firm in .275 (7x57).
The action is different as is the barrel profile or the front sight, and, even if the stock follows the classic lines of the early n°1, it's different too, being modernized with specific Dorleac' touches.
So there's not a problem for us to use and adapt a type A express rear sight.
While rebuilding that part, we have re-engraved the original digits markings and even if they are in meters the sight is perfectly regulated, at least for the two first leaves…shooting with that kind of iron further than three hundred meters invariably ends with the same results at three hundred yards !
Indeed, the barrel is clearly engraved with our own specific marking and the rifle bears French proofs marks, so it would be difficult to take it for a genuine Rigby.

DORLEAC
www.dorleac-dorleac.com