To give even more interest the 'Kilroy was 'ere' symbol - very similar to the one done by JohnB, above, is also similar to the schematic for the wheatstone bridge. (Can anyone confirm that btw?). Now then, the wheatstone bridge was invented by Prof. Wheatstone. - who also came up with the linkage mechanisms for various concertinas and accordians enabling them to use less reeds and more buttons! As well as being a prolific inventor he was also into squeeze boxes!

Gosh, I don't half carry a load of useless twoddle around with me don't I...

Cheers

Dave the Gnome