My first post - This Bag is 6 1/4" x 12", stenciled in large lettering "3-XII". It looks similar to some Reel Bags I have seen on the Internet, especially with the little metal 'acorn' swaged to the end of the drawstring, but this seems much larger than a Reel Bag, so maybe something else.
My thought is that it is a bag that would have held 12 oz. of corn mill or flour from an old water powered grist mill. I’ve seen similar ones made of burlap.
The symbol that looks like a “3” is one that was once used for the term “ounces.” And, it’s the proper size. See this link from a medicinal bottle collector site: