Part of the training for every one of my students was a circuit with the ASI covered. I remember one CPL student (not one of my regulars) who was very nervous when I told him what I wanted. He was doing quite well so on final I asked him what he thought the airspeed was. His response "65", I raised the post it note over the ASI and the indicated speed was 66.
After we landed he noted that was the single most confidence inspiring lesson he had ever had......