You may laugh at those signs today, but back in 1968 there was a movement to place a “THIS HOUSE IS NOT ARMED” in windows.
The sign fad did not last long.
Who is laughing? I was serious as a heart attack. I have an idiot next door neighbor and bought one of those signs to make a point. I did not place it but instead showed it to her from my yard. She almost freaked out, but she did admit she got the point.