[TXnMA]

Apparently cast iron. If they were bronze, I'd expect dissimilar metal corrosion to have consumed the iron crosspins. (BTW, those cross-pin holes look square, to me -- and, there's some sort of discontinuity where the axe poll joins the closed socket...)

~~~~~~~~~~~~~

I recall a (GGG?) article on a cache of similar-appearing bronze axe heads -- most/all of which were broken -- supposedly collected for re-casting. IIRC, by far the weakest points (sites of the breaks) were the sockets -- and, of those, the closed-end sockets were the weakest.

I believe one of the theories for the weakness was that it was difficult to get a close fit of the wooden haft in the closed-end socket -- causing local force concentrations (where the wood did fit tightly) -- that resulted in socket breakage...

Do you remember that article/discussion?

TXnMA   
  

[SunkenCiv]

That does sound familiar, didn’t turn it up in a search. Here’s something that’s basicaly unrelated, from 2011, well, technically it’s from more than 3000 years ago...

http://www.freerepublic.com/tag/tollensevalley/index