Since the fake documents played a role in opening those bank accounts at that time, they must be valid when withdrawing money later. What's more, the plot of the film is set in the 1950s. At that time, loopholes such as anti-counterfeiting technology would let many financial fraudsters get away with it.
Drama evaluation
The Shawshank Redemption is one of the most inspiring and satisfying films in 1990s. This is not only because it contains religious factors, and God never cares for Shawshank, but because it is a story of finding hope in the unshakable friendship between two people.
Crucially, as a chronological film based on Stephen King's non-horror short stories, this film has never been out of date. This is a moral fable, which is about keeping one's integrity and personal freedom under any circumstances. The same is true in real life, just like in this fictional fable.