Ghost sign

Our office landlord is planning on a bit of refurbishment and we have to contribute to the maintenance of the sash windows. I therefore decided to look up at them when I walked by this morning. Much to my surprise, I saw the ghost of some signwriting on one of the windows. It must have been the angle of the morning that made it appear - it's impossible to see from the inside.

As the weekly blip challenge is hidden, this has to be my entry!