I've been curious to know whether J. W. Pepper ever made another Sousaphone after building the prototype seen in the posts below. So far, I have found no evidence of that particular horn going into production, or even being made a second time. The reason may perhaps be the financial difficulties that faced the company in the 1890s (Paul Bierley mentions this in his outstanding work, The Incredible Band of John Philip Sousa, p. 56).
But it appears that Pepper did end up making other Sousaphones - at least eventually. Notice this page from the J. W. Pepper publication Everything Musical from the 1920s, courtesy of Mark Overton at saxophone.org:
You'll notice that at the top of the article, it says "The first 'Sousaphone' was named and built by J. W. Pepper over thirty years ago for Sousa's Band." This puts the publication at around 1925 - at which time the company was advertising the bell-front Sousaphone depicted here (for a mere $174.50!).