While reading on the net found this article.. thought I would share and see who has the answer..

.505 Gibbs Rifle Brass 'H H' Headstamp: Maker and Quality Info Sought

This .505 Gibbs brass, used in belt-felt .50 caliber rifle ammunition, is headstamped "H H." Do any Guns & Ammo readers know the origin of the stamp?

https://www.gunsandammo.com/editorial/505-gibbs-brass-h-h-headstamp/458742