Steel rebar is a product that most folks would consider to be pretty boring -- unless they work with concrete or survey land. When a survey plat or legal description specifies an "iron pin" either found or set, most likely that pin is a piece of steel rebar, so from the surveyor's perspective rebar tells an important story.
In their article entitled "How San Francisco Paid The Ransome", authors Chad and Linda Erickson share some interesting history about steel rebar, the invention and adoption (or lack of adoption) of various types of the product, and how the use of newer steel rebars in concrete greatly improved the integrity of concrete structures. Ironically, if the engineers of the day had adopted Ernest L. Ransome's new style of twisted rebar, more of San Francisco might have been spared from destruction by the 1906 earthquake.
From a surveyor's perspective, knowing the history of available steel rebars might provide valuable insight into the year that a certain property pin was set, thereby helping to validate the original survey markers. Read the full "Ransome" article in The American Surveyor at this link; we recommend using the link near the top of their web article to download the full PDF, since the included images greatly enhance the story.