Newbie question for Webley experts here!

I have a Webley Mark 11 Service, series 3. How does one remove the flip up aperture sight? The knurled wheel to adjust windage is on the LHS and not the RHS, and I wanted to swap it around, but it seems locked(grub screw removed).

Is it just personal preference as to whether wheel is on right /left or could it have left factory like this?

Thanks in advance