I found a dangerous fake in the wild today.
Here the Earth/Ground pin is partially insulated, which a real UK power plug would never, ever have. This is enough to know it's not up to spec.
The cable length itself feels strange, as if it's made of the wrong (unapproved?) type of material.
It's markings claim a 0.75mm wire, which would be good for no more than 6A of current, but the fuse claims to be 13A. So you could have a nice house fire if whatever this is plugged into shorts out.
I have no idea what country's wiring scheme these colours match up to. The colours themselves are super faded looking and are only a thin layer on some soft, easily cut mystery insulation.
The conductor is neither copper nor aluminium. It's much lighter in colour and very springy, you cannot twist it together. I am guessing brass? The resistive property is unknown (can't test rn), so even the assumption it's safe at 6A can't be trusted.
If you find one of these, cut both plugs off and throw it away.