Possibly a good opportunity to point out here that a 'test' genesis block with a different hash existed in
'the early Bitcoin sources from November 16, 2008 - a few months before the current blockchain began.' ... See:
Bitcoin source from November 2008.
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https://bitcointalksearch.org/topic/m.4108647Code extract from main.cpp ...
Bitcoin source from November 2008.
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https://bitcointalksearch.org/topic/m.4108739 //// debug
// Genesis Block:
// GetHash() = 0x000006b15d1327d67e971d1de9116bd60a3a01556c91b6ebaa416ebc0cfaa646
// hashPrevBlock = 0x0000000000000000000000000000000000000000000000000000000000000000
// hashMerkleRoot = 0x769a5e93fac273fd825da42d39ead975b5d712b2d50953f35a4fdebdec8083e3
// txNew.vin[0].scriptSig = 247422313
// txNew.vout[0].nValue = 10000
// txNew.vout[0].scriptPubKey = OP_CODESEPARATOR 0x31D18A083F381B4BDE37B649AACF8CD0AFD88C53A3587ECDB7FAF23D449C800AF1CE516199390BFE42991F10E7F5340F2A63449F0B639A7115C667E5D7B051D404 OP_CHECKSIG
// nTime = 1221069728
// nBits = 20
// nNonce = 141755
// CBlock(hashPrevBlock=000000, hashMerkleRoot=769a5e, nTime=1221069728, nBits=20, nNonce=141755, vtx=1)
// CTransaction(vin.size=1, vout.size=1, nLockTime=0)
// CTxIn(COutPoint(000000, -1), coinbase 04695dbf0e)
// CTxOut(nValue=10000, nSequence=4294967295, scriptPubKey=51b0, posNext=null)
// vMerkleTree: 769a5e
// Genesis block
CTransaction txNew;
txNew.vin.resize(1);
txNew.vout.resize(1);
txNew.vin[0].scriptSig = CScript() << 247422313;
txNew.vout[0].nValue = 10000;
txNew.vout[0].scriptPubKey = CScript() << OP_CODESEPARATOR << CBigNum("0x31D18A083F381B4BDE37B649AACF8CD0AFD88C53A3587ECDB7FAF23D449C800AF1CE516199390BFE42991F10E7F5340F2A63449F0B639A7115C667E5D7B051D404") << OP_CHECKSIG;
CBlock block;
block.vtx.push_back(txNew);
block.hashPrevBlock = 0;
block.hashMerkleRoot = block.BuildMerkleTree();
block.nTime = 1221069728;
block.nBits = 20;
block.nNonce = 141755;
. 
