I hate to say this, but "it depends"

Setting a hard rule like 10% or 70% just doesn't work.

Your chip is a *X value, so someone who really wanted an example for their collection would gladly pay more than 10% of the book for it. Maybe even 50%-70%?

If one finds a more common $10-$20 chip and the undrilled chip is out on the market, maybe 10% is a good number.

Chips that are commonly found drilled and scarce in undrilled state, would bring more, as that's the standard for that chip. Is the book on your chip for undrilled, high, because buckets of driled are out there? Back to 10%.

A good test is run it up on eBay and see what happens? Of course that can only be viewed as one instance. I've had four of a chip, and the first one went high (higher than I thought) second and third were reasonable, and the fourth had almost no bids and someone got a deal.

That brings up the question of how many people are really motivated to have a particular chip, in their collection?

Personally if I can't find a chip for my collection and I can find it drilled, I'll buy it, and hope that some day I find the undrilled version. Then I pass on the old one to someone else who is searching to fill a hole in their book.

Nice chip!