I'd grade it: Raw, on eBay, therefore: Probably fake, and possibly cleaned. With an expensive coin like that: why the HECK would nayone sell it raw!??!??
actually better put, but if you have a real coin and want to maximize the value (selling price) I would NEVER sell raw! Agreed, Kanga!
It's been awhile since I looked up the diagnostics on that key date. On first looks the coin itself looks authentic but I don't know without looking itup if the mint mark is added or not. Great Southern Coins has a decent return policy so if you got this I would run it down to your local trusted dealer and ask if he can help authenticate it so you could return it within the window they set. It looks to be Mid AU from the photos but the way the photograph these the glare hides most of the hairlines or other faults like cleanings etc... If it's RAW on e-bay generally it's not worth the trouble.
Sorry, one more quick note on key-date raw coins on e-bay. If it is not slabbed there is probably a good reason for that. GSC may suspect something like a cleaning so rather than have it in a genuine slab they may be hiding it with photography and taking thier chances with a RAW auction.