He didn't know but he felt like his Providence has regenerated to a degree for him to get his hand on this.
It will surely saved him a lot of things.
Under every item there as an explanation of things. This sachet was used by powerful entities including the ancient red dragon to kept their stuff hidden.
It was a good container that can hold one singular thing at a time. If two things were placed they somewhat merged or all got destroyed or one got destroyed.
What made it valuable was it indestructible nature as well as it was not directly part of the owner.
That was to say, Seth can jumped to sun and everything on him will be destroy and when he came out the sachet will still appear unharmed.
Every powerful figure that used it want it because in their dangerous world with strange abilities, things and arms got destroyed all the time during fight or dangerous environment.