I showed chatgpt the picture and it was close to what others on here said.

“The image shows a fused spur or a fused connection unit (FCU). This type of electrical outlet is used to protect appliances that are permanently connected to the electrical supply without a standard plug, such as heaters, ovens, or lighting circuits.”

Then I asked what country this is most likely to have this in a home

“The fused spur or fused connection unit (FCU) in the image is most commonly found in homes in the United Kingdom and Ireland. This type of electrical fitting is a standard feature in these countries, where it is used for appliances that need to be hardwired into the electrical system, such as water heaters, ovens, or extractors. It may also be found in other countries that follow British electrical standards, but the UK and Ireland are the most likely.”

I thought that was interesting and wanted to share.