https://www.gamespot.com/articles/call-of-duty-ww2-pre-order-bonuses-include-double-/1100-6453162/

Activision has released a new trailer for Call of Duty: WWII that shows off some of the bonuses that players can earn for pre-ordering the World War II-era shooter.

First, pre-ordering gets you the weapon of your choice right out of the gate on day one. This comes by way of a "permanent weapon unlock token" that you can apparently redeem for any gun you want. It seems like a pretty compelling offer. Unlocking weapons takes a bit of time, so if you want to start with something good right away, pre-ordering is one way to do that. The other big bonus for pre-ordering is that you'll earn double XP. This isn't unlimited double XP; far from it, as it only pays double for a period of four hours of gameplay. Still, that's a nice way to level up faster right away.