The only original flask I ever owned, with any kind of a ring, was a big old shotgun flask. It was British made, and had one large ring in the bottom. Hanging charger down, it wasn’t so likely to catch a live spark that way.
I have a replica military flask that has side rings, but, to be quite candid it scares the devil out of me. So, I took the shoulder strap off of it, and carry it in a pocket instead.
Hungry Horse