Sweet prize!! And what Brute Force is saying is that you had to do *something* that caused the gift. So the question becomes: where were you when you got them? To expand on Brute Force's answer in case you need the amplification:
- In the jungles of GE? (IMHO, the most likely place to see 100 Diamonds.)
- On one of the two guild-combat maps (GvG or GBg)?
- On the continental map -- the one you go to in order to fulfill quests & gain access to new boosted goods & expansions?
- In your city, after you clicked to fulfill a quest?
- In your city, after you collected production from a building like a Wishing Well, Fountain of Youth, or Hedge Maze?
As for a GB that can produce Diamonds, I want to know what it is!!!