The series of alloys made use of is stunning: weathering steel for patina, marine-grade light weight aluminum for weight financial savings
https://www.scribd.com/document/1041186672/Leader-Boxes-Built-to-Last-The-Architect-s-Copper-Requirement-135654
The range of alloys used is magnificent: weathering steel for patina, marine-grade aluminum for weight savings, and duplex stainless for rust resistance in severe climates.