Reader Lee (from www.coastaldiscoveries.org) writes:
I found a Neville Point spearhead dart along the Merrimack River in Newburyport this spring...
"...I found the dart during that "super tide" that we had in March. I think it was around March 20th. The Merrimack River had been dredged last summer and there are many new sandbars in the area and some of the older sandbars have disappeared. I wouldn't be surprised if the dart was unearthed during the dredging and with the very low tide on the 20th, it ended up on the beach right at the tide line."
Note: After some email exchanges, Curtiss Hoffman suggests this may be a "Mansion Inn" point from the transitional archaic.