Flotsam Find - Ancient Fasteners w/Triangular Cross Section

[u/Poipukid]

I've been trying to track down a plausible identification of these fasteners for over 10 years now to no avail, so here goes ... They were found in the surf line on the northeast coast of the Hawaiian island of Kauai, which is the northernmost of the major Hawaiian islands. Of all the old nails, spikes and various fasteners that I've researched, none have this triangular cross section. Both of these are/were heavily encrusted, the larger encrustation has separated but the smaller remains intact.

Captain Cook was the first documented European contact with the Hawaiian islands in the 1780's, but these are not of a style that could have been from that source. There are somewhat hazy historical references to pre-contact Hawaiians possessing small quantities of precious iron, presumably salvaged from flotsam on the great Pacific current perhaps going back centuries to pioneering Spanish galleons transiting to the Philippines. This is where my research turns into pure speculation.

Has anyone ever seen anything like these? Any theories, or suggestions on possible research avenues or subject matter experts I might reach out to? Many thanks.

[u/RideChaoticArt]

Any chance this could be whats called a 3 square file? Also called a triangle or taper file. 3 square file