Take the seal to a wholesale bearing supplier and they will measure the existing seal and then cross reference those measurements to a seal that will work. If you can give them the exact diameter of the shaft that will help because your seal is most likely worn where the shaft was riding on it.
Some of the metric sized seals will have a series of 3 numbers on them. The first number is the shaft size, the second number is the bore size it fits in and the third number is the width or thickness.
Clean it off carefully with some brake clean maybe, and the will be right on the face.
I worked in maintenance in a large monofilament company and most of our machinery was German made. Lots of metric bearings and seals on it.
Take the seal to a wholesale bearing supplier and they will measure the existing seal and then cross reference those measurements to a seal that will work. If you can give them the exact diameter of the shaft that will help because your seal is most likely worn where the shaft was riding on it.
a possible 'trick'.
If there's room in the hole for a 2nd seal, install it !
On one tractor the original seal was >1/4" thick(wide, deep,??). New seals were 1/8"+ thick so two seals could be installed. Extra seal ran over 'virgin' shaft.