 The most current thinking is that they were oil lamps, based on stylistic comparison with a 'cage' cup from Szekszard, Hungary, but may not be an entirely satisfactory answer, given that there seems to be no practical way of placing a wick in the cup.The only cup stemming from a datable context is from Cologne, and dated to the fourth century A.D.It is preserved in the Römisch-Germanisches Museum, Cologne.