We have a passion for putters at Goldhill Golf, so I love a good putting drill. I saw Andrew Coltart talk about this drill when discussing Scottie Scheffler’s putting improvement over recent times, and he used a pound coin, but in the absence of a clip from that exchange on Sky Sports, I’ve found a video using a quarter.
This works with the currency of your choice. Control your distance by controlling the length of your backswing and downswing, not the speed of your putter head. Give it a try and see if it helps you out there!