The earliest U.S. patent I could see was Clarence A. Godshalk, of Philadelphia, Pennsylvania, fliled in November of 1914, and granted in February of 1915.
The patent referred to the rib allowing for the heat expansion of the anchor points. I feel like I should know where Godshalk worked, it rings a bell.
Sorry, it was Fox of course. According to Bing, he and Edward Godshalk bought Fox out of receivership in 1912. Thats a long time before it's mentioned in the 1931 catalog.
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