Late to the party... only now noticed this section of the forum.
I wasn't aware they had North American-style socket type meters down under. I wouldn't mind getting one for my collection of vintage watthour meters, but seeing that this model had its approval pulled over a decade ago already, it's anyone's guess as to how many are left (presuming that the majority of meters down under get scrapped upon retirement).
I believe Doctorandus is correct as to the reason for the stippling on the disk - to help straighten and stiffen the disks (although one modern North American model, the Landis & Gyr MX, was produced with a smooth aluminum disk for a while).
As to the shiny spots on the disk, that's pretty unusual. The first thing that comes to mind is it could be a reflective surface for an optical pickup on the fixture used to calibrate the meters. All meters are calibrated under three load conditions - full load (100% test amp rating, 100% power factor), light load (10% test amp rating, 100% power factor), and power factor (100% test amp rating, 50% power factor). I'd assume that the calibration fixture would count how many pulses in a given interval - say 10 pulses for FL and PF, and 1 pulse for LL.