Roller-Blind Shutter

Roller-blind shutter. Wooden box-shaped object with an adjustable dial at the front, a mechanism at the back and a thin sheet of dark grey fabric in the middle. One side has a white disc set into the wood, with creation information. The other side has a five-digit number inscribed, possibly a serial number. A short length of string protrudes from one of the corners. There is a removable wooden square which is held in by metal prongs.