This game was released for the Commodore 64 in 1990 by Konami, which was another hugely popular game on the Nintendo NES.
The Commodore 64 disk of Castlevania did not have any copy protection on it, BUT instead you had
look up a password from the Castlevania Password Book. Like many code sheets from this time it was on dark red paper, making it very hard to photocopy. See below.
Thanks to Klotz, I was sent scans of the original sheet. As usual I converted it to Black and White and put into a PDF.
You can download it here: Castlevania-codes