Thanks for the link, I don’t recall seeing that message.
That explains the anonymized ICAO number.
However that email from @dbaker was from August 2016 and these are the first time I have seen them and I spend a lot of time looking at the Skyview screens.
I see aircraft in Skyview that are not shown in Flightaware.com because they have asked to remain private but these are the first that have been unidentifiable in Skyview. Why haven’t I been seeing it for the private aircraft for the last two years>
Police and Ambulance helicopters are still plainly visible. The Police are mode-S only and tracked by MLAT. There aren’t any other govmnt aircraft flying around here that I know of but enquiries are being made.
That is not a border; it is a beach on Port Phillip Bay which is wholly surrounded by the state of Victoria AU. The Maritime exclusion zone is 200NM off the southern coast. The only time Maritime Surveilance comes anywhere near this end of Australia is for the Avalon International Air Show in January.
Speed shows 38 Kt so it is either a very small/light plane or a helicopter and I am certain the a visiting Brazilian politician would travel all that way in something a bit more appropriate.
There is no TIS-B in Australia and if anyone is interested here is an Air Services (Australian equivalent of FAA) description of ADS-B implementation.
That seems to leave aircraft with privacy as the source but it doesn’t explain why I have only now started to see it nor why no-one else has commented on it.
If it becomes more widespread I’ll endeavour to visually identify the aircraft and work it out from there.