A handwritten signature commonly referred to as "signed by Stig Lindberg". This refers to the hand mark and the “G” part. As Lindberg's stamp of approval, the rest of the painting is done by the decorator in his workshop.
The G mark stands for Gustavsberg. Unlike the familiar anchor mark back stamp, it indicates that this work was handmade in the company's workshop. 
In this photo, "F98" is not the serial number, but the model number of the product (the initials of Figur, which stands for model). The trefoil mark is the signature of the decorator in charge, in this case “Anita Roi”. Gustavsberg had about 40 decorators.
Some pieces were painted by Stig Lindberg himself, but they are always signed by "Stig L.". So this sign should be called "supervised by Stig Lindberg".
Lindberg is a pretty heavy smoker and is almost always photographed with a pipe in his mouth. Perhaps because of this, I developed lung cancer in my later years and had to have one lung removed. After retiring at the age of 64, he moved to Italy, where he died soon after. He was 66 years old.
Even now, Lindberg's works are loved all over the world, but the number is decreasing and the price is soaring. Although it is expensive, Nordic tableware is basically for everyday use. There are many things that can break.
It reminds us of the past, when the Gustavsberg workshop energetically produced many masterpieces and worked hard with decorators.
