What was this bag for?

I've had this set that I use as a summertime fanny pack for around 40 years and I'm curious as to what it was originally for. I assembled this from a table full of similar items at a surplus store back in the early 80's picking the best condition of each. The bag attaches to a web belt and the shoulder straps as well with the hooks at the ends.

The only identifying marks are a very faded US on the bag cover and in the middle of the webbing of the shoulder straps. There are no tags numbers or manufacturers markings visible anywhere on either.

My questions are what was the bag originally used for, what era is it from and would the bag and shoulder straps have originally gone together? Thanks

Those look to be M-1956 pattern H harness shoulder straps and 1st pattern US Army M-1956 combat field pack AKA "Buttpack"... Nice shape too. Yes they were a set and there was the pistol belt and mag pouches too...and first aid pouch. Butt pack was utility for carrying an infantryman's stuff.

I used a set of those for a couple of years and preferred them to ours. Years later we made our own webbing that resembled that, just to prove the point.

Thank you Jim. Well how about that I've been using it for its intended purpose after all. Yes I have a pistol belt, holster and ammo pouch as well but I actually knew what they were. Don't have the med kit bag but I remember seeing them on the table. Unfortunately in all the time I have this set the belt has had to be replaced to an upsized one at least 3 times from the original I purchased back then.