It's your PS plaque. It symbolizes that you are in fact the Problem Solver. You leave it in your window on your door, so it distinguishes you from your neighbors. You always liked the initials. P and S. Pepper and Salt. Peas and Sarrots. Peaches and Sugar. You like these all.
Although originally you had a window in your door, it doesn't seem like there's a window there anymore. You don't know what this means.