The International Silver Company C337 mark appears on silver items produced by the International Silver Company, a major American manufacturer known for both sterling and silverplate wares. This mark includes the company name and the pattern or model number “C337,” which is used to identify a specific item within the company’s extensive catalog. The presence of this number helps collectors, appraisers, and historians date the piece and determine its design origin. While many items with this mark are silverplated, verification of material should be confirmed by checking for a separate “Sterling” stamp if applicable. The C337 mark serves as a reference point for authenticity, cataloging, and potential collectibility.