Pin firing is a widely used manufacturing process that allows china manufacturers to provide a fully glazed foot rather than a polished foot.
This process has the future china product going through the kiln on a mini stand which rests the greenware on “pins” so when glazed it does not stick to the kiln surface.
This process creates “pin marks” which reflect where the china rested while going through the kiln. These are completely normal, are fully vitrified, and completely non-porous.
Some examples of “pin marks” are displayed below.