That is a locking wheel stud, ie the thing that keeps the wheel on, not a locking wheelnut remover/key. There’s no completely normal reason for a kid to have one, but equally, it’s not useful for anything except keeping wheels on. At a guess, it’s volkswagen group but, that is definitely a guess.
So the absolute most nefarious explanation is that it’s a trophy or got dropped in a pocket while nicking a wheel.
But who nicks wheels? That went out of fashion before he was born probably. All the other explanations I can think of are random weird ones like “I found this and thought it was interesting”, but kids are weird. And the fact that people don’t recognise it, maybe adds a bit of probability to “thought it was interesting”? That makes it mysterious.
The T handle thing is pretty mangled, looks old? The split in the crosspin is odd. Gest guess is it looks like it might have been some sort of really low security lock, like a utility key, or maybe it’s something that’s been adapted for that/hammered into a utility lock? Like, I’m not sure it’s the right size for a white house external box that power meters go in but that sort of deal. It might just be the right size to get the inspection covers off an old street light, stuff like that. But as others say it can’t undo anything tight, it’s got no leverage and it doesn’t look strong. Dunno. It gives decades-old vibes, it totally looks like something my grandad’d have had in his toolkit since 1940 and he probably wouldn’t know what it was either.
