A 12th century Welsh document believed to be based on an earlier Dark Age War Poem, records Arthur's Sword as bearing 'a design of two serpents on the golden hilt'.
With the discovery of the historical Arthur, it is possible to make an informed speculation on the appearance of an historical 'Excalibur'.
Archaeology has demonstrated that the sword of a fifth-century British warrior would have been of the Roman spatha type - a Roman style cavalry sword, with a blade some 23 inches long with a stunted cross guard - NOT a huge, heavy broadsword of the Middle Ages, erroneously associated with Excalibur.
In a late Roman military document of the Western administration containing military insignia (circa 420), a shield bears the insignia of two crossed serpents. The design is the insignia of the Segontium Roman unit of the principle garrison in Gwynedd, the homeland of the historical Arthur. The Roman serpent, inherited as the tribal emblem of Gwynedd, ultimately became the red dragon of Wales.
If Arthur inherited a sword of office from his predecessors, the pro-Roman leaders of Gwynedd, it is historically feasible that such a sword would have born the motif of the double serpents, the insignia of the former Roman administration of the area. Gwynedd was not only the heartland of the imperialist faction in the late fifth-century Briton, but the dragon, or serpent, was its tribal emblem. It is, therefore, very possible that Arthur's sword would indeed have had 'a design of two serpents' on its hilt.