Looks like a normal sort of box with a hinged lid but your not in yet !!!
Inside the finder is confronted with a solid wooden block that can not be lifted out with fingers alone!
However there is a large woodscrew provided that can be tightened into the hole in the center of the block which will allow easy removal of the blockage, there is a suitabl hole on each side so the block can be returned any way up.
Beneath the block is a good sized clip top box containing logbook, pencil and a spare woodscrew.
Suitable woodscrews for mounting are provided.
Video Clip - https://youtu.be/LFZFxXM7C6E