The winning Oodlectible in the Diamond Hunt Oodlectible Game has an animated spotlight and shines on the coal, which shows a diamond poking out of the side that sparkles. Here is a screenshot of it:
If you have one or more of these animated Oodlectibles in your collections box, you will be credited in accordance with the rules. The prize team is having technical difficulties with the crediting tool though, and people will probably not be credited until Wednesday. Thank you for your patience!