Proof of Existence — first OP_RETURN (DOCPROOF) notarization

First DOCPROOF-prefixed OP_RETURN timestamp in the scan. NOT the first Proof of Existence proof — the service began in 2013 with an address-encoded method [[proof-of-existence-genesis]] and only switched to this OP_RETURN/DOCPROOF format once OP_RETURN became relay-standard (March 2014). Self-discovered; not yet chain-verified.