I don't think it's a chain either.
I can't think of any reason to have a link with such a large cross-sectional diameter, and then not be fully welded at the ends.
Like they say: A chain is only as strong as its weakest link.
I agree with the other posters that these are most likely just large lock washers.
And not stainless or galvanized either. (Intended to be painted, or used indoors / out of the elements.)