It is detailed instructions about what to do in a gas attack in 1943. I suppose it needed to be posted during construction of the house.
Clicking and enlarging the jpeg will make it readable.
Also, there is a reference to a 'sealed room' that people were to retreat to and seal themselves into in the event of a gas attack.
And noted at the bottom, evidently you could buy war bombardment insurance.
Three antique thumb tacks held it in place. I remember seeing this style in the drawer of my Dad's desk when I was very young. They were a simple disk with a triangular punch-out that had been bent at a 45 degree angle to make the point of the thumbtack. An elegant design.