Which specific anchor design featured arms that were cast in one piece and pivoted at the crown via a bolt?

Answer

Lieutenant Rodger's anchor

Lieutenant Rodger's anchor, developed post-1852, was refined so that the arms were cast in a single piece and attached to the forked shank by a bolt passing through the crown, allowing them to pivot.

Which specific anchor design featured arms that were cast in one piece and pivoted at the crown via a bolt?
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