This is an original Power supply for the Sinclair ZX Spectrum +2 (the grey one). Probably once stocked by a Sinclair repair service, as they were in a shelf without single packing. They are absolutely new, unused and without plugs. You can connect the suitable plugs for your country.
The power supply can be used for Spectrum +2, but also for Spectrum 128, Spectrum Plus and Gummy Spectrum 48k. Of course you can use this power supply as well for any other machine that needs 9V, but be aware that Sinclair always put the ground on the inner port of the plug.