Well yes it did exist! The stand for it remains today, but the sundial and direction finder are long gone.
The Thames Star 30 January 1973 featured an article about a 'fact' on one of the indicators.
The plaque claiming the arrival of Captain Cook to the area in 1869, when as the Kelly family pointed out should have read 1769.
I have seen photos of people standing by the sundial - if you have one please let me know.
Below is a 2016 photo looking towards the Peace Memorial. The base of the sundial still stands today - lower right.
Update 17/2/2017: 1972 Group of people enjoying finding places on the direction finder.
View of Thames, Firth of Thames on right.
G. Riethmaier (R24805249)