This item appears to be a magnifying glass but the glass is concave rather than convex. It does not magnify, it only makes things look smaller.
I believe that it is meant to be used with teetotum type spinners that were popular in the early to mid 1900's. The only markings on the Nickel plated frame is "Made in France".The 6-sided brass Put and Take spinner included in this sale spins perfectly on the concave glass surface and falls withen the metal frame. The glass is 2 1/2" in diameter.
I took a YouTube video that can be seen by loging in to You Tube and doing a search for "concave glass for teetotum".