Sapphire watch crystal tester (1-off)

Details

I bought this as a sample. It tests to see if a "watch glass" is made of plastic / glass, or it if is made of sapphire.

I'm not sure why anyone would want to know this.

My only guess is that very expensive watches are made with sapphire whereas forgeries will use plastic or glass.

So if someone is offering you a Rolex, and you know that they are made with sapphire, and it tests as not-sapphire, then you have a forgery (that's my guess, anyway).

Takes three AAA batteries.

NOTE: this does not work on gemstones.