A player’s share of the clan rewards depends on their ranking in the final clan quest stats. The higher a player ranks, the greater their reward.
Coins and rating points are more “valuable”. If a player does well enough to acquire a chest rather than just coins and rating points, then the player may receive a drop of various playable items from the chest. It might contain items, books, scrolls or boosters.
Different playable items have different probabilities of being dropped from chests. This probability is shown in the chest info. To view the chest info, tap the Chest icon in the Battle Participants and Rewards list.