Coming back to your picture of the gearbox.
I have been searching now for my gearbox sticker but it was difficult to read because this sticker was at baboard side of the gearbox.
As far as I can see the manufacturer is "Hurth" and the type should be "HBW-20-3R". Type HBW-20 is for sure but the ratio (3R) is guessed only because so hard to read.
However it is the same gearbox you have. The oil type is ATF-A and the oil quantity should be 0.3 liters. On top of the gearbox is no ID plate but only the ATF-A sticker.
Amel Sharki #60
Currently Kalamata, Greece