Looking Back to 2014 and Playdead's Limbo | TheXboxHub
The extra hidden secret eggs in Limbo that is not unknown to many (read description for explanation of this. I provided a link to the Youtube video showing them being collected) :
Limbo Secret Level + DING! Achievement - YouTube
Steam Community :: Guide :: LIMBO - All Hidden Egg Locations and Achievements
The Secret Level In Limbo That You May Have Missed