[Please use the forum image uploader for photos. Thanks. Tom]

Lee Wulff rods had the cork cut that way, and if looking for a source for such a book, that's where I'd begin.
I'm thinking this has more to do with indexing reel position rather than grip comfort.
Think I'd look at South Bend Comficient grip and PHY variations on cut cork grips for the comfort aspect.

This is Andy's interpretation of Lee Wulff cork (on the rare Lami 605)

the rod has beaver cork - if you wanted a collectible, you want one with a hang tag still on it.
What you have is a rod to fish, and it has the karma of having been fished by the original owner.
There's nothing there that affects the value of the rod - if his reel indexing affects your ability to fish the rod, that becomes a disappointment for you.
It was his rod before, just like it's your rod now.

Here's one I sold to a big-time Shakespeare collector in NFLCC. The rod had no use to me to fish when put next to my others, and I thought it belonged in his collection.
After he received it, he said the blade and handle don't match - I was certainly fooled - they look pretty perfect to me, and the ferrule fit perfectly. But apparently his catalog showed different.