There are marks on the harmonic balancer's outside edge, the best thing to do if you can, is start the car and with the engine running reach under the front on the engine with a wire brush and apply that to the rim of the rotating harmonic balancer, that will clean of any rust and/or grime. Then you can stop the engine and rotate it so that the markings are facing downwards, clean the area of the markings with acetone or paint thinner to completely degrease it, once that's done get some bright paint or her best nail polish, paint over the markings and then wipe the area off. That should leave residual paint down in the stamped indicator markings and it will make it 1000% easier to see the marks when you need to!