its totally random and if you think about it, the items inside shouldnt change. i would think that the devs/mods make 5mil+ chests toghether putting random items in random chests, just like skittles. (the skittles term was stolen from a thread in sl drops from mobs) the higher the chest value, the higher the chances of dropping a good item. if you reach into a skittles bag, and they put less green than red because more people like green than red, they buy more than one bag so they can get more green skittles. if you open a chest, and you get what you want, its a green skittle. if its garbage, its a red skittle. thats why more chests drop before a new update, because they need to get rid of as much of the skittles as possible. hope this wasnt too hard to read.