It was only in March of this year that I really wanted to know just how old this sign really was. So I dug around came across these sites in Wikedia (London Postal District" - Wikepedia, "N.E Postcode area" - Wikepedia).
I was actually rather fascinated at the age of the sign (and there are more dotted around the East End! just look up from time to time). Apparently, according to Wikepedia, the postcode came into use around 1856 till 1866 when the area was merged with the 'e' postcode (look around Brick Lane, and you will still see the 'E' suffix signs still up). London at that time, got so big that they had to portion london up into different postal codes instead of having one big system as you would for a town at that time.
This is really an interesting piece of postal history and a relic of the time.
Check back often, as I will be adding more images of signs from this time period.