A tin filled with plaster and a key is used in Recruitment Drive during the Miss Cheevers challenge. It is one of the 9 stages of tins used during the quest. The tin with the bronze key is created by heating up the tin filled with tin and copper on a bunsen burner found in the room. It should then be used with a knife, chisel, or bronze wire to retrieve the bronze key needed to complete the challenge. Using the wrong ingredients can result in a useless tin (strange).