Have you ever been looking at a listing and it is says the book is remainder marked? To this you are completely baffled wondering what exactly is a remainder mark. Here is quick guide to the explanation and some history of a remainder marks.
Remainder marks are generally simple; they often look like random dots or streaks from a black or colored magic marker. Remainder marks vary from the tactful, to the gaudy, to the look of being accidental.
The purpose of the remainder mark is when a store does not sell a book they mark the bottom or top edges. The remainder mark is put onto the book and sent to a distributor to make room for new inventory. Then the distributor will re-sell them for a discount rate. That is why when you see a book with a remainder mark it is usually for a discounted price. It's a way that distributors tracking the book once it leaves the store that way a store can't return a book for credit. From a collectors stand point a book that is Remainder marked is not worth as much as a copy that is not. The Remainder mark that is on top edge of a book is worse from the stand point that you can see the mark when shelved.
Some publishers do this as well, for example Ace Fantasy uses a capital "B" on one edge. Simon & Schuster, uses its logo "the sowing man". Random House uses the icon of a little house.
During the 1980's Publisher's with such names as Doubleday and Delacort used a dye to spray over the top and bottom edges. This generally led the book to have a spray painted look to it.
Remainder marks vary from each place that uses them, but you can always tell if you know what you are looking for.