What is this?

[footfootfoot]

Originally Posted by Flint

Yes, double-stick tape, markings at 1" increments. The question is: why?

well markings like that are often used to plot points on an xy graph for lots of applications, transferring or scaling drawings is one type of application, depicting data is another. Why a circle? What is circular besides drum heads and cymbals? (and besides, scaling and transferring drawings this way is terribly retro) Windows can be circular, game boards could be circular.

But why the tape? why does this need to be carefully taped/registered in place?

Something to do with checking the area of rectangles or other shapes? Some type of measuring device?