Specimen jar is an item that is obtainable during The Dig Site quest. It is used to find charcoal from a specimen tray. It is obtained by searching sacks in the Digsite, or by searching the cupboard on the south wall in the west room in the Exam Centre. In the dig site quest, it is also used to dig in level 1-3 areas which would be a vital part to finishing the quest.
After the quest this item is still obtainable from the Exam Centre (south wall cupboard) 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.