Abstract: A rigid container package, such as made of tin, metal, etc., having an interior for holding particulate material, such as food stuffs (like coffee beans), under vacuum, and which includes a mouth to be opened to provide access to the contents of the package. The package is preferably formed from a rigid material in the form of a container, such as a tin box, and has affixed thereon a one-way pressure-equalizing valve. The valve preferably includes a displaceable rubber disk located on a valve seat and is arranged to operate such that any gasses within the package are allowed to vent to the exterior of the package, by passing through the interface between the disk and valve seat, while the ambient atmosphere is substantially precluded from entering into the interior of the package. The disk then engages the valve seat to isolate the interior of the package from the exterior. A layer of silicone oil or similar material is preferably provided on the disk to facilitate operation of the valve.