Dave, I'm no expert on Rookwood pottery, But I do know what the Roman numeral stands for. It's the year of manufacture. The company first marked their pieces around 1886 and a little flame was added around the Rookwood logo for each year up to 1900. From 1901 on up the date was indicated with the Roman numeral. So the piece you show, LVII, is from 1957. The other number below that is a company mold or design number. I never could understand why they could have two different spellings of "Glenn". These images are from Larry Trapp's collection. It looks like there are different colors of the Rookwood tray.