British people, if you have a weird callous on your dominant hand's index finger palm side, starting at the second knuckle outer edge and then going in a straight line diagonally down and across.
Thats because of Coca-Cola changing their bottles to the "attached caps".
For the cap to stay attached after opening they had to reduce the height of the cap by about 1/3rd which means the torque you now have to apply whenever you open or reopen the cap damages your hand.