Before 1853. Taylor's Joseph Lang rifle, made in 53, has a 2 leaf, express sight - thus, standing sight and 2 extra leaves. 100, 150 and 200yards.
Exact earlier dates, I do not know. Maybe Mr. Bob Roller has some ideas on this.
That this rifle was build about 1853 - this type of sight must precede that date.
In 1860, Forsyth wrote about "our intrepid purchaser, raising the 500 yard blade and squinting over it at a coolie pulling a cart and saying, I hope to meet a tiger soon. I feel this will be quite a smasher for him" - or words to that effect.
