What are the possible drops for defeating Yeti Zombie?

A Yeti Zombie spawned in Ancient Egypt for me just now, and the game says I should try to defeat it in order to obtain fabulous treasure. I killed it in the game and got a lunch box, containing just one normal key (useful for unlocking). I don't think the prize is THAT awesome. Is that all?

What are the other possibilities for Yeti Zombie drops?

Killing Yetis can drop multiple lunchboxes.

Each lunchbox can contain either keys or diamonds.

http://plantsvszombies.wikia.com/wiki/Treasure_Yeti

The lunchboxes always contain 1000 coins.

Since gate keys are no longer in the game, and diamonds have been repurposed as a premium currency, this is currently the only thing you get from Yetis.