I am certain that Zelda 1 on the NES has clocks preventing Wallmasters from coming out of the walls, and 99% certain it had no multiple clocks.
The item sets work a bit differently than ZC. I believe the item is somehow related to the number of remaining enemies. I saw an article that someone made when doing a TAS that explained how it worked. Long story short, the RNG is abusable.
EDIT: Here's the page I was talking about. Slice it and dice it, it should give you much more accurate item drop behavior:
http://tasvideos.org/2091S.html
