It's a macro lens and wide angle lens for your cell phone. The macro lens lets you take extreme close-ups (handy for photographing coins) and a wide angle lens lets you view a wider shot, say 120 degrees instead of, say, 90 degrees. Not very helpful for photographing coins, but helpful for taking selfie group shots for example.
it has a built in uv light I guess it helps with detecting counterfeit paper money. It actually helps me with determining MD vs true doubling cause it takes the glare of led lighting away.
That sounds like something I need alright... Now how to get one... Someone can delete my post above this one, done by accident
There's lots of them for sale on Amazon, eBay etc. Here's one example: https://www.amazon.com/Zeso-Professional-Fisheye-Samsung-Universal/dp/B018HB1GUG I hope I don't get in trouble for posting a link to an external website! Just trying to help out a fellow coin enthusiast.