As I've read it, HIN's in our vintage were not required nor standardized until late late production, if not until after production stopped or in the early 80's. I venture to say that it is very unlikely to find a second or third HIN aboard a WS of any make.
That being said, it is recommended to have your COD number in 3 locations. 1 may be decorative and readily seen, but then the other 2 ought to be possibly glassed into a bulkhead, floor-board, or keel so that it is extremely difficult to rid the boat of COD and makes it much easier for the owner to recover if stolen.
T.