Difference between Gen 1 Gen 2 maruader

Gen 1 has the trigger further forward, pistol grip is more vertical and trigger further back on Gen 2. If it has a synthetic stock or synthetic adjustable cheek piece it's a Gen 2. 

And the stocks are not interchangeable between generations without inletting work, so you don't have to worry about a stock change fooling you. There is one other subtle difference If you're trying to to tell the difference in a rifle with a custom stock. On the gen 1 - If you look at the receiver left side, along the bottom edge there is a notch where the bolt retaining screw can be removed to pull out the bolt. the gen 2 was redesigned to have a switchable left/right bolt, so this isn't there.