Poppy Trail denotes Metlox pattern name. The same basic mark was used with a number of different patterns made by Metlox, with just the pattern name changing as applicable.
Additional Note from About.com user Anastacia Gibbs: "Many of the original Metlox marks which look similar to this one and are authentic are smeared. We have many pieces with this mark that belonged to my husband's parents and they were purchased here in California when the factory was still active."

