I want to get one of these.     I've never actually seen anyone wearing one in real life before (you see guys in Scandanavian metal bands wearing them occasionally).  I'd imagine they're probably more common over in Europe than here.      They are meant to be worn out over your shirt, but I think I'd prefer to wear it hidden, under my shirt.     I'm not looking to impress anyone with it.    It's just for me.  
I'm sure it's not everyone's cup of tea and most people would think I'm a weirdo, but I pretty much am a weirdo, so that' ok.      
https://wodanesdag.com/pp-hamr.html