Vintage German motorcycle jackets sizes

[KURGAN]

I'd like to add to my collection an old German motorcycle jacket. I like so much the ones made by Harro brand, they were very well made and had an amazing look. But a thing that i don't understand very well are the sizes. Some have numbers similar to our Italian sizes (but are a bit different) and some other (maybe the older ones) have very high numbers such as 98 or so.....
Does anybody here have some experience with old school German jackets sizes?

Thank you in advance!

 

[Roughwear]

You might get a better response if this is posted in the Moto section.

 

[KURGAN]

Anyway, it seems that nobody knows anything about those old German sizes. I'll try to buy a jacket i like, i will ask the seller for some measurements.