I was having trouble communicating with my wife the different grind settings I had dialed in for Espresso and Drip coffee. Since we only have the one grinder, we go back and forth through the day. 

This fits right under the wooden holder for the dosing cup, and swings around to show the different setting. There is an arrow around the letters E (espresso) and D (drip) to show which way to adjust the grinder. 

To mark it up I just use a black dry erase marker. It comes off with just my thumb!