Since writing an article in 2015 describing the unsatisfactory performance of the GPZ 7000 in some of WA's iron rich areas several events have occurred.
First, the 2015 communication with Minelab was unsatisfactory, their response was to seek more training!
As a consequence, I sold the machine as both vendor and Minelab refused to take back the machine.
Incredibly a week later Minelab announced and supplied the yellow iron dust toroid and a procedure to "balance" the machine. This device and procedure cancelled the effect of the X signal which was apparently making the machine "deaf" to small nuggets in some of our WA iron-rich grounds.
Minelab subsequently came up with software/firmware modifications which have further improved the machine.
I have recently purchased a second machine and take care to carefully perform the recommended procedure with the yellow toroid and to also carefully perform the ground balance for the G signal. I also recheck these settings every hour or so as in some areas they drift off.
The yellow toroid is fragile and will easily break in two when dropped. Glueing the pieces back together makes the toroid usable again. It is the mass of the iron dust particles which is important.
While I am now satisfied with the GPZ 7000 performance in WA I still regret the hassle and lack of meaningful support from Minelab. They should realise that customers talk and sometimes may be right.