I once spoke with a fellow who designed a sight like this and do believe he only made one of them, for his personal use.
I understand what you mean about rotating the lens and seeing the numbers on a clock face. This fellow's sight lens did the same thing,...but he did it for a reason, and intentionally.
Background info,...this was about 1965 or '67,...recurve days,...the guy used a tab with, of course, a finger release style,...anchored under the chin,...similar to champs of the day, Clay Sherman, Jim Caspers, Dave Keagy, etc.
He shot a very light bow,...maybe 30# for target shooting at ranges up to 100 yards,...also, he had a short draw. This ment when he adjusted his sight to it's lowest setting for long range shooting, he could not use it for 100 yards. The sight would not go low enough without interferring with the arrow's passage. But, if he used this lens that bent the sight line he could do it. The aimimg lens would be located higher on the sight bar, bend the light rays for aiming, and the arrow would not be deflected by the sight.
I'm not sure i explained this very well. But I completely understand the sight you have and how it was used. It was designed to allow the archer to shoot greater distances with lighter weight bows. I am guessing it is from the 1960s or thereabouts. Probably a good item for a collector.
Hope this helps. This is my take on it. What do you other fellows think?