Evidence like these fittings clearly shows the electrics in this house are old and substandard. Even if everything looks modern: new light switches and sockets, modern residual current device consumer unit etc, there could still be hidden shortcomings such as a lack of earth bonding.
When you are buying a new home always get the electrics checked. If you already own the property you should think about asking a registered electrician to give things the once over about every five years. Better safe than sorry.