In the UK all Eggs (from a source with over 50 hens) are stamped identifying whether they are organic, free range, from barn or caged hens. The stamps also show the size of Eggs and a code identifying where they came from.
I believe some parts of Australia require Eggs to be stamped, but it is certainly not the case in New South Wales (though a few particular brands do seem to have stamps, it is very rare). It bothers me that when I buy Eggs from a shop, I don't really know that they are the box describes. I've often had Eggs that don't seem as fresh as the box would indicate – I wonder if I've ever had caged Eggs that were in a free-range organic box? How would I know?
Whilst it would add an extra cost to stamp all Eggs, I don't think the cost would be prohibitively expensive. It would be a small price to pay for the assurance that the Eggs you paid for are the Eggs in the box.
Would you also like to see all Eggs sold in Australia stamped with the date, source and type?