John
How do you think the market would react to a card graded say PSA 8 but where the seller subsequently disclosed that it had been chemically enhanced by him?
I've only had a restorer work on one card (ungraded old judge of pop smith, born in Digby NS where my spouse was also born) and when I eventually sell it, will make full disclosure)
I've had a number of books restored (mostly missing front endpapers or split hinges) where the restoration should be obvious, and again, I have and will always disclose.
Here's the latest candidate for restoration, a 1948 Japanese language edition of The Babe Ruth Story. . Might have to turn the H2O up to 11 on this one