Vintage French 18k Gold Tubogas Coil NecklaceA vintage French tubogasstyle coil necklace with a tightly wrapped serpentine construction that runs in a continuous line around the neck. The ribbed coil design gives the piece a flexible, fluid quality while still maintaining a structured, collarlike silhouette when worn. The necklace is stamped Brevet S. G. D. G., a French patent mark that was required by law between 1844 and 1968, supporting a mid20thcentury dating. The goldtone metal retains good