An inscription found at Birdoswald in 1821 is now displayed in the small site museum (RIB 1905). It had previously been displayed in the undercroft at nearby Lanercost Priory (and where it features in Charles M. Daniels, Handbook to the Roman Wall 13th ed.).
The altar was dedicated to the ‘holy god’ Silvanus, and the dedicators were the venatores or hunters of Banna. Banna is almost certainly Birdoswald, and is a name also known from the Rudge cup found at Froxfield in Wiltshire (for the replica, now in the British Museum) that shows some of the forts along Hadrian’s Wall.
It has been suggested that the inscription should be dated to the 3rd century (supported by David Breeze in his Handbook to the Roman Wall).