Heres more German practice for Jawa.
Although from a Rieju it probably also applies to the unit referenced above by Mr Luke as they all seem to use the same one, but usually in black, which might be the safest buy. Apparently there were different ones for different export markets, eg some with rev limiting to 10,000 rpm - obviously not a consideration here!
Only the first and last columns are relevant. It looks as if the advance curve is almost flat, and only slightly retarded from the reference setting.