===================================
L2J
19 00                     // p.len 25
2E                        // pcode
01                        // always const
42 55 77 8F  C3 05 69 87  // xorkey first part
01 00 00 00               // always const 
01                        // possible Game Server ID // on L2J always 01
00 00 00 00               // always NULLs
00 00 00 00               // in L2J always NULLs - no obfuscation

==========================================
Retail NCSoft
19 00                     // p.len 25
2E                        // pcode
01                        // always const
42 55 77 8F  C3 05 69 87  // xorkey first part
01 00 00 00               // always const 
01                        // possible Game Server ID - depends on game server ID
00 00 00 00               // always NULLs
XX XX XX XX               // always different, non-nulls: opcode obfuscator
 