What device is this plug for?

Installed a load of cameras a long time ago and while moving a camera I came across this plug in my box of bits.

Now for the life of me I can’t remember what this is for. I’ve tried looking at the product pages for all the different devices I have but can’t see anything even close. Before any asks it’s 100% a ring plug as it has Ring on the moulded plug.

List of devices I have are:

Doorbell
Flood light cams
Spotlight cams
Stick up cams
Indoor cams
Alarm system with various door sensors and a motion detector

Hi @Shortbottom. This looks like it is the Outdoor Power Adapter. This should connect to the Barrel Plug end of your power adapter.