Installing piston pin lock rings

[georgesgiralt]

Grease the thread. Then apply it to your thumb and measure the space between the marks on your thumb. If there are ten marks, and you measure the total length, measurement will be more precise.
As thread pitch comes in finite and precise values, you round the measurement to the nearest DIN value and you're good.
Bear in mind that German manufacturer used DIN norms which very often converted directly to ISO but not all the time. So if you search for the thread pitch and size of the measurements you make, you'll be good.