Yes and no. Typically gate marks show that the piece is older 1880ish or earlier, but not always. As in life there are exceptions. Spiders for instance, were made up to the 1950's and at least one foundry, Glascock for example, had gate marks on theirs throughout that time. Another example is recast items. This is were an original item is used as a pattern, a mold is made and then poured through the bottom leaving a gate mark. The last examples are larger items, like wash and sugar kettles. Being so large they were hand molded and typically were cast from the bottom, sometimes with multiple gate marks.