old MONARCH FINER FOODS lion logo glass jar

This old glass jar with original metal screw on lid holds approximately a gallon (I think?) and measures about 8" tall and 6" square. It features the MONARCH FINER FOODS name and lion's head logo on its front (?) with a series of decorative angled ridges on its sides and a blank back (?) side. (maybe for a long-gone paper label?) On its bottom is a maker's mark consisting of an 'I' within an oval/diamond with the numbers 7, 6, & 3 surrounding it. [does anybody know what all that means?]

I don't know what it would have originally held (coffee, maybe?) or exactly how old it really is -- but my Mom has used it as a storage canister in her pantry during my entire lifetime (until it has now become mine) and it was already "old" when I was a kid -- so I'd havta guess it dates from the 1940's-50's at least.