CIMRM 593-594 - Very early tauroctony. British Museum
From: Picasaweb. By Geoffrey Heriot.
From here. By Ferrell Jenkins.
According to Manfred Clauss, "The Roman cult of Mithras", this item belongs to the first quarter of the first century. It has been heavily restored, however.
Note: the last sentence refers to Vermaseren's belief that earlier Zoroastrian monuments are "Mithraic". This would not be taken for granted today.