I enquired with the Perth Mint regarding the dies used to produce the current batch of 1992 Kookaburras being distributed, to my relatively untrained eye, the new coins appeared to have finer/thinner details particularly in the branches and leaves above the kook's head. Here's the response regarding which dies were used: So basically differences depending on the age of the individual die sets used to strike a particular batch of coins.
Speaking of die quality the strike on a recent dragon privy I got was so weak that the queens had no gills at all... I'll see If I can get a photo
http://www.eons.com/groups/topic/2524936-One-Tough-Bird One Tough Bird Kookaburra survives 435 mile trip stuck in car's grille Only thing that can kill a kookaburra is the Perthmint's marketing dept.