If the Model 660 has the original stock, the checkering is impressed with heat and pressure which makes it flat by it's nature. In essence it's reverse checkering. Where raised diamonds normally exist, they actually are indentations into the wood. Impressed checkering is a cheap way to "checker" a factory rifle. It's functional but not a true checkering job.
It can be cut to reverse everything but it's probably not worth doing it in terms of cost.
