This altar was discovered in April 1852, subsequent to the 1850 excavations of the east gate of the Roman fort at Lympne in Kent (RIB 66). The inscription shows that it was a dedication to the god Neptune, set up by L. Aufidius Pant(h)era who was serving as the praefectus of the British fleet, clas(sis) Brit(annicae).
Pant(h)era, from Umbria, served as prefect in a cavalry unit in Upper Pannonia and is named in a diploma dated to 2 July 133. He probably moved to Britannia subsequent to this date.
It appears that the altar was reused in the later Saxon Shore fort, probably dating to the second half of the third century. The altar was purchased by the British Museum from Charles Roach Smith in 1856 (inv. 1856.07-01.5026).