A container includes a housing and a cover which may be wholly or partially removed to open the container. A foil seal is used to seal the joint between the housing and the cover. The foil seal is internal to the container. The foil seal separates during opening of the cover, respective parts of the foil seal remaining with the housing and the cover. The foil seal may be a metal or metal-containing foil, for example being an aluminum, steel, or titanium foil, or a metalized plastic foil. A cutter, such as a serrated edge, may be positioned to facilitate cutting of the foil seal during cover opening. The container may be part of a seeker assembly with the housing being a seeker housing, and the cover being a removable or hinged cover that protects an optical seeker during some portions of flight, such as during launch of a spacecraft.