the times i have went picking liberty caps i would have id'd those in the picture as 100% positively libs. i've never seen any mushrooms (in scotland) that look close enough to liberty caps for there to be a false id. there was one type of mushroom that looked kinda similar but without the nipple, it was rounded at the top and didn't have as dark an underside as lc's.. and after some googling the imposters turned out to be edible anyway (if i remember correctly). don't know what grows where you are so if unsure it's best to be careful... but i would personally take the shrooms in that pic though, without any hesitation.