This is a classic from Swiss design house, Gubelin, circa 1990. I love the Mid-Century vibe! 

It features two 3-D fish in a circular setting. It measures 24mm diameter (about the size of a quarter) and weighs 5.72 grams.

On the side is an engraving, "Leon 16.3.65". Of course, you can always have your local jeweler buff that out.

If you search the web for comparable products, you'll see that this is a much better deal.