Vavers were very spendy sights, and very rare today! They sold originally in the early 1930's for $12.50, which was more than a lot of the guns they went on sold for! Very accurate, and extremely well made! I'm amazed that they could make such a fine sight with the equipment at that time. I'm guessing a fair amount of hand fitting was required.
I have an old "tang sight" that is built to accept a modified Lyman 48. It has a single thumb knob to remove the sight, and the base and Lyman sight are dovetailed with parallel slots to give perfect alignment when returned to the base.
It's the 3rd one in from the left in this picture. Made with a base to fit Ballard rifles:
