Abstract: A hermetic enclosure assembly, having utility for preservational storage and/or display of objects susceptible to degradation by exposure conditions such as ultraviolet radiation, visible light, oxygen, humidity, microbial, fungal, and insect species, internal acidity and external acidic gases, and the like. The enclosure assembly includes a gas-impervious housing, a mounting base, and a back cover plate, with an oxygen indicating means in communication with an interior volume of the enclosure assembly, and a slow vapor-released deacidification medium being arranged for dispersing deacidification medium vapor into the interior volume of the enclosure assembly. Also disclosed is an appertaining method of preservationally and protectively enclosing an object for storage and/or display. The invention has particular utility in the storage and/or display of cellulosic objects, which are especially susceptible to embrittlement and decay at low pH conditions, in exposure to visible light, oxygen, and moisture.