...
You can use a plastic earth pin on items which are double insulated.....but any metal earth pin must have no sleeving unlike that shown in the pic!
The reason behind the no sheathing is because the whole setup is designed so that when inserting and removing a plug the earth contact is the first to make and the last to break. As a result, some older wall sockets have the earth contact very close to the surface and on the item in the first post, there is a risk that any item connected using this lead would not have any earth connection at all because the conatct in the socket would be sat on the insulated section!
That’s the EXACT reason I looked closer at the plug! Basically a PC in our shop gave me a tiny tiny shock every time I plugged a monitor in! This was due to the sleeve on the earth pin, as it connects when first plugged in, but once the plug is seated properly, the earth contacts in the socket are touching the sleeve only!

Got a bag full of these leads upstairs! And that’s not including the few which I’ve just taken off the shelf in the shop itself!
