Pottery & Porcelain Marks – Arrows: Arrows have been used as marks since the early 19th century, about 1828, and are still used today. Earliest marks are a line with an upside-down v-shaped symbol on top. Later marks have two arrows, usually crossed, with a few lines jutting outward on each side at the bottom. These marks appear most often on earthenware, but they also appear on art pottery and stoneware. Harker Pottery Co. is one of the main producers of 20th century American pottery with arrow marks.