It is to determine a measure of theis liquidity that judges jerk an egg past their ear when judging listening for a tell tale 'flip'. If shaken too vigorously, however, even a fresh egg's contents can move withing the membranes. At shows where no barriers are placed between the exhibits and the public, winning eggs can be shaken by all who pass with the result that the end of the day they too will 'rattle' and the judges reputaion is held in dispute. Fresh eggs, when sent to a show by rail or parcel post, also tend to end up rattling on the show bench. I have often been surprised when judging, when a fresh looking egg has rattled - 'fresh looking' might sound subjective, but tot eh practiced eye there are considerable differences between fresh and stale eggs.
Brown eggs take on a dull almost greenish hue when exposed to bright light for any length of time.
White eggs often develop translucent patches in their shells with age and all eggs lose their bloom becoming dull and lifeless. When faced with a fresh looking egg that rattles I break open, as empowered to do by Poultry Club rules. A large air sac, runny white and a flat yolk with wrinkled membrane would indicate age. Assuming evaporation has taken place and that the now enlarged air sac is at the broad end, the egg will float broad end up in a pan of water, only those whose appearance gives a reason to doubt freshness.