Some quick images from Google Images : "Aztec Sword"
Search them yourself .
Form follows function .
Note the counter balance at the back of the hilt and the room for a double-handed grip . They were also known as sword-clubs . But obsidian is so sharp (still used in surgical implements - monomolecular) . But it is brittle . So it was used in a swiping fashion . Hence the double-handed grip .
But after a hard day's battle , the sharp obsidian chips would have fractured away and you were left with a club . This is what happened to the Aztecs and Incas against Spanish steel .
But make no mistake , a swipe will eviscerate you without even feeling it . Indeed , some think that the sharpness of the obsidian blades combined with the low speed of pain-nervous impules (see http://andreswhy.blogspot.com "Memristors,bloodpressure and click") is responsible for the Mayan and Aztec fascination with scarification and subcutaneous depilation . They did not feel the pain immediately , and even then it was spread out .
European weapons for Nobility also had a rounded edge in front , edged with obsidian shards for that extra little bit of close-shave . Note that the workaday weapons of the Aztecs as shown above did not have a tip . Too easily worn away . The Spanish tactics of points for a sword must have come as a rude surprise .
Weapons development :
Europeans tacked on a durable front edged bronze point and gradually extended the bronze down to the hilt , then substituting iron and then steel , ending with the sword as we know it . Tactics adapted to suit .
I have not seen such a bastard-sword , and I think it will be extremely rare and valuable . The lobe at the tip of the Cerne Abbas sword hints at it . So look at burial sites near the battle .
Probably in some museum classified as a hollow-point dagger or something equally silly . (The wood would have rotted away.)
The popularity of the Arthurian legends took everybody by surprise (including the authors .)
But they were simply following a time-hallowed route followed by musical composers and other artists . Take an existing folk-song and embroider on it . Memory in pre-literate societies were kept by bards in chanted mnemonic forms . Cf Homer . Real events get concentrated and simplified , but still have a real core .
So it it is no wonder Ur-Arthur resonated with Artorius .
The requirements are a hopeless war , but some victorious battles and a promise of hope in the future , usually embodied in some enduring artifact like a sword .
Ur-Arthur seems to have fought a valiant slowing-down action at Cerne Abbas , enabling the existing stone-age peoples to have enough time to adapt to the incoming flood of Bronze-age civilization peoples . Hence the emphasis on the Stone Sword .
The battle was probably a draw . Equivalent battles (cf Ramses II , Ramses III) gave rise to long-lasting accords because nobody won decisively .Like a guerilla army , Ur-Arthur only had to avoid defeat to win decisively .
And the Lady of the Lake ?
There is usually some core to legends . Look for a ditch , lake or body of water near the then site . Ur-Arthur was probably killed , and his private retinue ran away , ditching their weapons in the process . But both sides were so exhausted (and Ur-Arthur wasn't in the loop) , so the survivors could make a durable peace .
Of course , he was then then immediately near-deified , being safely dead .To such an extent that the echoes lingered on for at least 5 000 years .
Sic est gloria .