In the early 1900s thirteen engraved Conus shell valuables were dug from prehistoric midden mounds in Oro Province. Since the early 1970s nineteen undated surface finds have been found in the northern Massim of Milne Bay Province. When three artifacts became available for AMS radiocarbon dating, provided they were restored after sampling to their original visual appearance, a specialist team was assembled and this paper reports its findings regarding the thirty-two shells. The paper covers sampling and conservation, dating (including new information on the local oceanic reservoir effect), distribution, art, depositional and cultural histories. These distinctive Conus shell valuables are part of the material culture found along the northern coast of the eastern tip of New Guinea and on the islands of the northern Massim during the Expansion Phase c.1000-500 BP. Their decoration is comparable to that produced by Milne Bay Province woodcarvers in historic times. This continuity makes them the oldest radiocarbon dated artifacts decorated in the Massim art style.