Vivian Cambell anyone? My guess is they're based on the Seymour Duncan Invader pickups that he used in his Les Paul during his early days with Dio. I can remember the interview all the way back in issue 2 of guitarist magazine around 1983!! It's stuck in my mind ever since then, although Bare Knuckle pickups weren't around then!! Built for the Les Paul then!!! :D
the HD is based on the Duncan JB
I don't think Vivian had an invader in his main les paul
he had a regular looking zebra pickup in the bridge and some kind of blade pickup in the neck position (looks like some kind of early dimarzio x2n)
later that year he swapped the bridge pickup for a black one
I have no idea what models were they, but I know he used Dimarzios in early 80's
the album tone sounds a lot like a super distortion + marshalls to me, and that's what the first version of the BK Holy Diver model was based off
but it could be a JB, since he used that and the duncan custom in several guitars too
the newest holy diver model does not sound like early Dio with Vivian at all
more like Doug Aldrich or late Craig Goldy
the cold sweat model already covers the early 80's tone pretty well, so I guess Tim wanted something to fill that medium high output ballpark with something that could do classic and modern rock without forcing that 80's edge
the cold sweat and nailbomb are very edgy and aggressive pickups, so he probably wanted something stay between that and the bluesier medium hot models like the abraxas and crawler
the "new" diver was actually one of the rebel yell prototypes