Here you can see the F Mark how they look originaly on porcelain from the early 1750 up to 1780. The F Mark was painted on porcelain for the Manufacture Fürstenberg beginning 1753. Earlier Pieces , before 1753 are also existing but they are difficult to identify. They can be identified if they have the shape from Fürstenberg Pieces of the mid of 18th Century. Some of them have
incised letters which could help to identify them as well. I own only one Piece
from this period of the manufacture.
All the F Mark are very different. Because they where painted from many different workers in the manufacture.
The first two examples showing how completely different marks can be.
This explains why you cant date a porcelain only with the mark.
You have to look at the painting , the glace,the porcelain and the mark. This together can give an idea from which time of the 18th Century the porcelain could be.