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…
Bayonet Mount Outfits Acrylic
Bar Outfitted with Bayonet Mount
Bayonet Mount Hook
Bar Merchandiser Plugs-In
Large-Bore Plug-in Hook
Hidden Hex-Key Mount Faceout
Round Faceout Fits Square Hole

Moving farther afield browse…
Plug ‘N Play Jewelry Display
Wood Inlay as Point-of-Purchase Display
Basketball as a Seasonal Theme
Tree-Like Display Sports Metal Faceouts
Hat Ledge Plugs In
When to Use a Permanent Hook
Baseline Post for Plug-in Hooks
Plug-in and Pegboard Hooks Combine
Plug-in Hook of a Different Sort

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