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There are numerous accounts throughout GoT where a Valyrian steel sword has been shown, followed by someone immediately identifying that the sword is made of Valyrian steel.
How are they able to so quickly tell the composition of the sword?
Do Valyrian steel swords have a special marking that's imprinted by the smith? Or, are people able to tell simply by knowing what different metals look like?
To me it seems kind of unusual that so many people know what Valyrian steel looks like when it's said to be such a rare metal.