Bob, I think the blob top bottles you're referring to as becoming obsolete around 1880 are the ones that were designed to take a cork. The ones you're showing I'm pretty certain were lightning stopper bottles, and those were used much more recently, and only invented in the mid 1870s. These wire stoppers never really stopped being used, so it would make sense to me to see blob top bottles in the early 20th century. Apparently Henry Putnam's company, one of the major US suppliers of lightning stoppers, continued selling them until the early 1920s https://sha.org/bottle/pdffiles/HenryPutnam.pdfThanks, Bruce
As you probably know, some bottlers used Hutchinson bottles well into the 1920s. So it isn't surprising that the Willms brothers were possibly one of those bottlers. But what is surprising are their blob-top bottles. Its hard to imagine they used that type of bottle in the 1910s and 1920s - although I suppose its possible. By the way, does the finish (lip) on your Willms bottle appear to have been applied after it was originally made? And is it hand-blown or machine made?
Here's a similar bottle with a lightning stopper: https://www.worthpoint.com/worthopedia/full-old-el-husting-milwaukee-wi-blob-weiss-beer