Mystery Photo III was 'miles from home' - readers were asked to identify the location of the milestone below, that appeared to be 11 miles (it looks older than 1966) from Sydney.
Of course, if you'd seen the other side, or had some idea of Sydney geography, you may have realised that it was actually only 2 miles from Sydney - and 13 from Parramatta.
That knowledge may not have been enough, even armed with a map and a protractor - or Google Maps - to locate it accurately. One gets the impression that the milestone may well have been moved sometime over the last century, given how neatly it snuggles into the recently landscaped footpath and garden.
So where is it ? BM-dog guess it accurately - with lots of help from Marrickville Greens, who identified - via the vegetation appropriately enough - that it was somewhere near the Parramatta Road side of Sydney University. In fact it's on Science Road in the shadow of the Main Quad - E16 on this map.
If there are any historians from the Uni reading this I'd be interested in hearing the history of the milestone - my guess is that it was salvaged from Parramatta Road at some stage (construction of the Footbridge Theatre maybe) but this is pure speculation.
When in doubt - google ! This Sydney University heritage page lists 'Milestone Sydney II' - uncertain if it's an original or a copy - but definitely pre 1900 and if orginal relates to an 1810 Macquarie Road. Take a look at the listing. There's also a 1995 conservation study of Milestone I (Parramatta XIV) available at Sydney Town Hall by appointment.