a packaging for an implantable medical device such as a heart valve wherein the implantable medical device is immersed in a liquid medium . the packaging comprises ajar and a lid assembly having a seal and a ridge therebetween , the ridge being adapted to contact the seal . at least one circumferential leg is interposed between the lid assembly and the jar . the leg maintains a predetermined spacing between the lid and the jar and may be loaded in compression . the lid assembly may comprise a lid and an overcap . the overcap may turn independently of the lid and may apply compressive pressure to the lid over the ridge and seal . the lid and overcap may be coupled together by , for example , mating snap hooks . at least one of the lid or overcap may have a plurality of snap hooks . at least one of the plurality of snap hooks may be of different length than other of the snap hooks , whereby an asymmetric force may be applied to the lid when the overcap is loosened from the jar .