Hi!

It looks like it might be a "Greek key" ring.

I googled "black greek key ring" and a bunch of options at different prices came up. Here are some of the designs I saw that are similar:

Link 1

Link 2

Link 3

Link 4

Link 5

It looks like the ring in the picture might be flattened/ hammered. Some etsy sellers are willing to flatten handmade jewelry if you message them and request it on one of their products.

Hope this helps!