Include assets decrypted and unpackaged from different client versions. If you want to open the models, you should use Urho3D (game engine used by them).
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Decrypt Algorithm
Code:
static const std::vector<int> PTM_DECRYPTKEYS = { 0xDE, 0xAD, 0xFA, 0xCE };
for( unsigned int i = 0; i < iFileSize; i++ )
pBuffer[i] = pBuffer[i] ^ vKeys[i % vKeys.size()];