@ChrisBlank Beat error is the clockwise and counter-clockwise rotation of the balance wheel. With zero beat error both rotations will be equal. Anything below 0.6 is acceptable, but I prefer 0 or close to it. Some people will accept higher values and I'm a hobby watchmaker and not a master, so other opinions will be welcome. For my watches I set timing and beat to a few seconds fast per day @ zero beat error. You will need a timing machine and to learn to make the adjustments. It's delicate and tedious, but fun if you enjoy nerdy things