The John Deere 1051 PTO is an Austraian designed and made harvester.
If you want to see one in action, then have a look here;
https://www.youtube.com/watch?v=ngrUxJzmFGQ
This is one of many old tractors and accessories you can see at the Tractor museum.
This particular piece of machinery sits just outside the Museum, so can be accessed easily.
You'll the cache hidden on the one part of the harvester that isn't roped off!
Whiteman Park is open 8:30am - 6:00pm year round, so this will not be accessible outside those hours.