One way to tell if a porcelain box is an antique is to look for a manufacturer's mark placed on the porcelain under the glaze or paint. Another identifying mark is a particular image or small written logo from antique manufacturers.
Certain productions of porcelain boxes had artist marks etched into the glaze. Other importers or design houses stamped their names and the dates of production onto the bottom of the box. When a design house commissioned a specific artist, he would leave his signature or initials somewhere on the box. In addition to signatures, small studios and individual artists often added hand-painted decoration to their work, from decor and highlights to specific images. Occasionally, the entire design was painted by hand.
If the manufacturer's mark is on the top of the box's glaze, the box is usually much less valuable. Some antique porcelain boxes do not have markings on them if created before 1891. That was the year custom laws in the United States changed and required a country-of-origin marking on porcelain goods. If there is no identifying mark or manufacturer's stamp, have the piece evaluated by an antique dealer or analyst to determine the likelihood that it is an antique.