This is the front half of a Tenax fastener. Common on older convertibles for securing the tonneau cover; they are small spring loaded catches opened and closed by pulling up on the small metal knob. My Ferrari has two of them to secure the fuse cover to the dashboard.
Unless you happen to know that you have to pull the knob up to refasten, you will probably push hard enough on the knob to crush the mechanism inside. This is what has happened to both my fasteners.
Here is the rear half of the connector. One of the three jaws inside has been crushed backwards meaning that the fastener no longer grips properly and needs replacing.Replacements come in two flavours: British Tenax fasteners and German Tenax fasteners. As expected they are not compatible so correct identification is important. My fasteners are marked with ‘GHE’ on the front and ‘33’ on the back meaning my car is fitted with German fasteners. Replacement ‘Small Head’ fasteners have been ordered from EagleDay.com, along with the special tool to fit them.