**Note:** In the full history of the XRP Ledger, there is an exception to the rule that transaction hashes are unique. Two early [SetFee pseudo-transactions][] had the exact same fields, resulting in the same hash, `1C15FEA3E1D50F96B6598607FC773FF1F6E0125F30160144BE0C5CBC52F5151B`. The first of these transactions appears [in ledger 3715073](websocket-api-tool.html?server=wss%3A%2F%2Fs2.ripple.com%2F&req=%7B%22id%22%3A%22setfee_nonunique_hash_1%22%2C%22command%22%3A%22transaction_entry%22%2C%22tx_hash%22%3A%221C15FEA3E1D50F96B6598607FC773FF1F6E0125F30160144BE0C5CBC52F5151B%22%2C%22ledger_index%22%3A3715073%7D) and the second is [in ledger 3721729](websocket-api-tool.html?server=wss%3A%2F%2Fs2.ripple.com%2F&req=%7B%22id%22%3A%22setfee_nonunique_hash_1%22%2C%22command%22%3A%22transaction_entry%22%2C%22tx_hash%22%3A%221C15FEA3E1D50F96B6598607FC773FF1F6E0125F30160144BE0C5CBC52F5151B%22%2C%22ledger_index%22%3A3721729%7D). Newer [SetFee pseudo-transactions][] include a `LedgerSequence` field so that they are guaranteed to be unique.
