It will be salmon (AKA pink) or black Alps in an AT101-series Dell, never white, unless it's had a switch transplant. AT10xW will be black Alps. It's interesting that this is an AT101W in Britain, as it should be AT102W (the ISO version).
I got an unused (new in plastic bag!) AT102W and it was disappointing. It didn't feel tactile or linear, just a sort of strange in-between. It was almost spotlessly clean (just a spot of paint on it) and having found a graph by SPARC of black Alps, his graph closely resembled what I was feeling. There's a second bump after the first one, like you get with simplified Alps and Matias switches, but a lot worse.
It's a nice chassis, but you'd probably want to replace both the keycaps and the switches.
White Alps, I have no idea, as they vary so much between the keyboards I've got. They're far stiffer than MX blue, and they need a good strike to move, instead of the soft touch that Cherry MX accepts. You get a far better click out of them and a deeper sound out of all Alps switches.