Strictly for post WW2 vehicles. Useful site if you are thinking of having a bash at your own rules.
Armour levels are given as "line of sight" (LOS) figures. If you are unsure what that means, it is the amount of armour a projectile will need to pass through to achieve a penetration. For instance a glacis plate angled at 60 degrees roughly doubles the amount of armour a gun will have to punch through.
http://collinsj.tripod.com/protect.htm
Cheers, Rob :)