1851 R. G. Latham in Tacitus vi. 36 (note) In Gothic archaeology it is well known that the so-called metallic age is separated from the so-called ante-metallic by a broad line of demarcation.
1885 F. Hirth 302 Broca..has..drawn attention to the traces of trepanning executed by means of stones on human skulls found in graves of the ante-metallic period.