Bashford Dean was the most notable of American armor aficionados of the early 20th century. He formed the collection at the Metropolitan Museum in NY, first as unpaid curator and then as the first paid full time curator of Arms and Armor. He was very much a child of the Victorian Era whose academic training was in Zoology. He was, in fact, curator of Reptiles and Fishes at the Museum of Natural History in NY when approached to help out at the Met. The Victorian mindset was that "Things lead to things". We are all familiar with nice neat tree diagrams that depict how the Advanced Races developed from the Savage Races. In any event, Dean brought that thinking to the study of Arms and Armor and one result were the sort of charts which follow depicting the stages of development of various armors and elements thereof.
While one might take issue with some of the implications of these diagrams, they are very useful as a handy-dandy way of seeing what occurred when. I also include Dean's nomenclature which one might compare to that of the nomenclature chart that I posted earlier.
These diagrams are ca. 1915 and were meant a descriptive pieces for vistors to the museum.
Dean was a prolific writer; I show about 97 books and articles in my inventory. Interestingly, few of his writings appear outside of Museum publications. His collection catalogs of objects at the Met are must-haves for any Arms and Armor library. His first Handbook to the collections at the Met was published in 1905 and grew as the collection did with editions in 1915, 1921 and 1930 (posthumous). I think that 1930 was the last issue but I could be wrong. Any one of these makes for a good read since Dean had both a daunting command of his subject as well as the English language.