[Fred Nerks]

If proved to be authentic it will lend weight to the theory that Spanish or Portuguese navigators ‘discovered’ Australia’s eastern seaboard centuries before Capt Cook...

no it won't, it will only prove someone dropped a coin...

Here's my favourite prior claim to Australia:

Facsimile of chart from Nicholas Vallard's manuscript sea atlas (1547), now held in the Huntington Library, San Marino, California. The facsimile was given the title "The first Map of Australia from Nicholas Vallard's Atlas, 1547" by the publisher, in 1856. The original chart was produced in Dieppe, France in the 16th century, and was thought to represent Portuguese charting of the northeastern coast of Australia.

Don't ask me about the camels, the horses and the large feline...not to mention the very Balinese-looking buildings and the elaborate clothing of the 'inhabitants' - Australian aboriginals went naked and the umbrella would have terrified them!

[SunkenCiv]

I’d be very surprised if Australia hasn’t seen landfalls by many different ships from many different cultures going back thousands of years. The idea that the ancestors of the aborigines got there by boat and that no one else ever found an entire continent until fairly recent times is, on the face of it, kinda ridiculous, IMHO. :’)