Those pictures are at least ten years old, and taken I think with an old video camera. The ladder on my sight does not move. The aperture carrier moves on the ladder. It's similar to an attachment for the "Singer" rear sight for the No. 4 rifle. that was made by A.J. Parker or Parker-Hale, I forget which. When I have some slack time I'll drag them both out of the safes and take better pictures.