Marathon Digital Holdings (MARA) recently changed its name (it was Marathon Patent Group). They've also switched up their methods, they now mine and hold Bitcoin (BTC). 

It's a tough one to analyze as all of their gains are unrealized, meaning that they have no real revenue or profit figures, but that doesn't mean it isn't a good investment. As valuations increase, their balance sheet will appear better and better.   

The key difference between buying this and straight-up buying bitcoin is that you're believing in their ability to continuously scale-up and mine more Bitcoin. But be careful, you don't always know what's going on with these and you're also heavily reliant on the Crypto Market.