The wine fermenting slats have a beautiful red-ish tint, which goes as deep as an inch and a half into the wood. It’s random and fades in and out, so makes for a nice effect.
Bill’s right on the treatment, but, as he indicates, it should be obvious, until the wood is nearly not worth chasing.
I note the value of pallets change from place to place. For us Pacific Northwtners, pallets from the east offer a lot of oak, for example. Others offer up a lot of poplar.
When in doubt as to if staples or nails have been completely removed, I resort to my sanders. Other than having to avoid sparks in a vacuum/collector, there is no danger of damage to blades.