A glass or antiques expert can verify the age of the glass. Valuable antique glass is characterized by signs of wear, defects and rough mold edges.
Antique glass typically shows signs of wear on its base and in any gilded decorations. Different types of small scratches at varying depths indicate the glass was used over a long period of time.
Defects such as chips and bubbles are common in antique glass. Chipping can signify age, especially if the chips have differing degrees of sharpness and shininess. A sharp, shiny chip is more recent than a smooth, dull chip. Bubbles are typical in old pattern glass, not cut glass, though they also appear in modern glass, sometimes by design. In general, new glass has fewer bubbles than old glass.
Two other signs that glass was made using out-of-date methods are grit and asymmetry. Antique glass made from molds might contain grit, whereas modern glass does not. Some old glass also has an asymmetric shape from uneven cooling.
Pressed or molded glass often has seams that show the edges of the mold. In early methods, glass molds were clamped together until some of the glass oozed out, leaving rough seams in the glass. Modern methods also create mold seams, though they are much smoother than in antique glass.