This ingenious plug-in hook imitates a BNC Connector (aka British Naval Connector among other names) in attachment. The rotating collar backplate is a male bayonet mount with pin. The display socket is a female mount with matching groove. The male is inserted and then rotated to lock the pin (and entire hook) in the groove.
For interesting alternatives see…
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“Bayonet Mount Hook“
“Bar Merchandiser Plugs-In“
“Large-Bore Plug-in Hook“
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“Plug-in Hook of a Different Sort“SEARCH “Sock” to follow the product thread.