Specimen jar is a members only item that is obtainable during The Dig Site quest to find charcoal from a panning tray and to dig in level 1-3 areas. It is obtained by completing the third test during the quest or by searching the cupboard on the east wall in the west room in the Exam Centre.
After the quest this item is still obtainable from the cupboard within the Exam Centre and is needed to search the specimen tray to try and find charcoal or other various loot. If a player does not have a specimen jar in their inventory upon searching the specimen tray the message "There must be a workman present when you are searching the tray." will appear in the chatbox.