What characteristic most enhances the value of glassware at auction?

The characteristic that most enhances the value of glassware at auction is typically the presence of a signature. A signature on glassware indicates that the piece was crafted by a specific artist or manufacturer, which can significantly increase its desirability and market value to collectors. Signature pieces often come with a known provenance and assurance of quality, rarity, and craftsmanship, all of which contribute to a higher valuation.

In contrast, while size, age, and color can certainly influence value, they don't universally guarantee the same level of appreciation as a signature does. Size may impact how a piece is displayed or used, age can suggest historical significance, and color can affect aesthetic appeal, but none of these factors inherently provide the same cachet that a recognized artist's or manufacturer's signature does. Collectors typically seek authenticated pieces that stand out in terms of artistry and heritage, making the signature a key identifier of value in the auction market for glassware.