I'm currently looking at Celtic coins (http://www.celticcoins.ca/) in hope of finding something with CAS on... there are thousands of 'em... they sometimes show the heads of the kings (I think the Casse one on the EB loading screen may be the wrong head, by the way - I found the same pic and it's actually an unknown ruler of an unknown tribe http://www.celticcoins.ca/record.php?coin_id=000846 ) I've only managed to find CATTI (Dobunni, Severn Valley area) which may or may not be connected, but mostly what I've found so far are other snippets of information - coins generally have an animal of some sort on one side (in the case of the Catuvellauni it's usually a horse) and the head or a mint mark on the other (CAMV for Camulodunon appears frequently, and almost always with an ear of corn which seems to be the town's emblem) There are also some pictures of a mounted warrior which are worth looking at - they are seen with carnyxes, lances, javelins and swords, sometimes in mail, which on one coin appears to include sleeves, and helmets with a noticable brim. The coins show that the Britons had contacts with other cultures, as there are images of Artemis, Pegasus, sphinxes, lions and even a Persian style winged figure on some.