Langbar International

Andy
I think that you'll find that the plate is a standard hebrew attachment called a mezuzah

They date back to the time of Pesach (passover), when the jews were in exile in Egypt. They were commanded to slay a lamb in sacrifice and mark the door with the blood. Then according to old testament, when God 'passed over' and slew the first born of the Egyptian families, he ignored the houses with the mark.

All Jewish homes are supposed to have mezuzahs at the door and at the entrance to every room, except the toilet and cupboards. They are now metal plaques, sometimes with a piece of scripture inside and checked to be kosher.

Quite normal in north London.