The listing, Magnifier and more has ended.
It's a magnifier, a bookmark, a metric and inch ruler.
From the National Lung Screening Trial.
7-1/2" x 2-1/2 " overall. The magnifier portion is 3-5/8" x 2-1/4".
Ruler is 4" one side and 10 cm other side.
It has crescent cut out to clip it to a book or page.
Comes in a plastic sleeve to protect the lens.