NOTE: Bill Banks 2020: ref Heacock Book 9, p68 (photo).The pattern is called "Melon Rib Swirl". Millers patent for the Swirl design in 1888 described the technique used... a rib spot mold and then twisted it. Shortly after the patent was received, spot molds were made to create the raised swirl design which eliminated the need to twist the pieces by hand. The bottom of this piece shows the indentations made by the metal plate that was used to anchor the ball of glass while it was twisted to get the swirl design. Then it was finished off by blowing into the melon shaped mold. Heacock believed this to be made by Northwood. Shown in book 9 pg 68. [..]the early plate marks on the bottom it would date to 1888 or earlier." known in blue, vaseline, cranberry