The black base to an Ashton Drake Stand
Soften the head by warming in heating pad for about 30 minutes. While the head is still soft and warm, push it down over the stand knob where the clear stand attaches. What you are attempting to do is to enlarge the hole (it is only temporary).
When the head is cool and solid again, pull it off the stand and you will have greater access to the knob. Use the pliers by putting the pointed end into the hole in the button and it pries out rather easily. Just reheat the head, and it goes back to normal for attaching to another body!