Found your registration number in 1899 advertisement.
It`s actually patent number for electroplating innovation described as `` most perfect and durable in the area of silver plating``
`` reinforced silver deposit on tines and resting areas a,b.c ``.
It seems that the name of the town (Geislingen) was more important than WMF trade name at the time.
That would explain ``Geislingen`` mark on your fork.
Hoping this helps. It was really exciting to discover the meaning of the patent.