Authenticity of Plato's Republic

[damonish]

How certain are we that the text of Plato's Republic is as he wrote it? (I am not talking about translations, but the bedrock version written in classical greek)

[Wyman]

How certain are we that the text of Plato's Republic is as he wrote it? (I am not talking about translations, but the bedrock version written in classical greek)

Don't know. But he lived to a fairly old age and these dialogues were published and well known during his lifetime, I believe.
They were also heavily studied by immediate successors and students - Aristotle among them. So I would think that any variations on the original text would have been ironed out and the text standardized pretty completely by the time of his death.