Well, probably not all that old, compared with some of the stuff you'll find on this blog. But -- it's been around for a while.
According to this site, these plaques have been around in America since the 1980s at least. You can buy them online still. Somehow, North Shore City have decided to keep this by the Devonport foreshore, beside the footpath leasding to the wharf. For what reason, I don't know at this stage. Perhaps a reader could shed some light on this. Are there any in Australia?