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 a jar 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.