I have a very good condition Seiyaryu, and since I have recently Quit Yu-gi-oh I was price checking all of my cards, but when I looked for the code for the card, I soon figured out that the card didn't have the right code, the code is SDD-E001 which doesn't match any of the codes that I saw, I know it is legit because I got it with a Yu-gi-oh video game when I was little. Does anyone know how to price it?

as far as price, I am pretty sure what Psking said is accurate. as far as being legit but not matching any set identifiers here, that particular card was released in the UK, signified by the E in the set ID. if it had been released in the US, there wouldn't be any letters to the right of the dash, as cards released in the US did not start featuring the language ID until well after dark duel stories for gameboy color was released.