New Zealand plugs produced since around 2005 are required to have partial sleeving on the pins:

That's the black bits on the pins above. Depending on the manufacturer, that could also be white or some other colour, but black is common. The earth (the vertical pin at the bottom) must never be sleeved.

Plugs prior to 2005 weren't required to have it, so usually just had three bare pins - these are still legal to use, but not for new equipment.

If the plug is partially inserted, you can potentially touch the pins while they are live, or a coin/tape measure/other metal object could hit them. The insulation stops this as by the time the metal part is out of the socket, the pins aren't making contact inside any more and are dead.

It's not a massive hazard (they were legal a while ago) but it's a sign that it probably doesn't comply properly with any of the other safety rules.

The Regulatory Compliance Mark (RCM) is an Aus/NZ equivalent of the EU's CE mark, and certifies both electrical safety and electromagnetic interference:

I believe it's also meant to have a number starting with an N attached, to identify the manufacturer/importer.

It's fairly recent, so older gear might have a C-Tick instead, which was only about electromagnetic interference.

A lot of gear will also have a smattering of other logos and a manufacturer's name. If you only get the words 'AC/DC ADAPTOR' and a picture of a house, be worried.