In the 1960s, early '70s, arrows were sold as "for bows up to" some poundage--35, 45, 55 etc.
No one even used the term spine before the 1920s and then they didn't mean only stiffness. The term came to it's current meaning sometime after the mid 1930s, when Klopsteg and Hickman and their fellow experimenters were threshing out the concept.
Howard Hill is said to have shot a new batch of arrows to see which ones went where he wanted them. The ones that didn't, he broke so they wouldn't get mixed in with the good ones.
With no spine tester, Horace Ford set a record in the York round in 1857 that was not beaten until 1943! Spine, swine, wish his score was mine, to hark back to Charlotte's Web.