Help my son idetify this language/alphabet

[Oakmaiden]

My son found this painted on a wall when he was out for a walk. He has spent the morning researching runes and alphabets, trying to work out what it means. We do recognise the upper symbol as being a pre runic symbol (Futhark) for the letter Z, but that may be a coincidence.

Anyone seen anything similar before? It was painted on the wall next to a door...

(reposted with new title, on the suggestion of another poster)

Is it a graffiti tag SE on top and JO on the bottom?

There wasn't anything else on the wall, just this. It was next to a doorway to a flat above a camera shop. So in between 2 shops, effectively.

I thought it looked a bit like it was done with spray paint and a stencil (hence the marks to the bottom left and top right)

It looks like a stencil to me too

SE JO- looks like a tag/graffiti