The earliest shell gorgets date back to 3000 years BP. Archaeologists speculate they were used either for gorgets or headdress ornaments. Iconography on the shell gorgets comes from the Mississippian Ideological Interaction Sphere. As early as 1688, regulations provided for the wearing of gorgets by Swedish army officers. Mussel shell gorgets, dentalia, and abalone were prized trade items for jewelry. Engraved gorgets appeared in the late Hopewell. Also in the cache were two "Cox style" and two "Nashville I style" gorgets. Initially, Hopewellian peoples carved plain shell gorgets around 1000 BCE. This harp and crown motif was prevalent on the Volunteer companies flags, belt-plates and gorgets. Numerous other pairs of extremely similar gorgets serve to link sites across the entire Southeast. Some Citico rattlesnake gorgets are also found late in the Clover Phase in West Virginia. As Mississippian shell gorgets were traded widely, common designs have a widespread geographical distribution. Coiled rattlesnakes gorgets were found among the Guale Indians of Georgia. Calusa people of southern Florida harvested and carved gorgets. Lightning whelk ("Sinistrofulgur perversum") is the most common shell used for gorgets.