Perhaps it was deemed acceptable in a non-mainstream publication as this, but I was still taken aback by seeing an actual toilet pictured in an ad from 1920. (If you'll recall your growing up years, movies and TV shows couldn't show or even imply toilets existed. Unlike the anything goes world of today, it was a big "moment" to hear Archie Bunker flush his toilet on his show in the 1970's.) So, more than likely, this photo is from a plumbing supply catalog of the day. But it was still a surprise. And seeing how the retail price of this city directory was $10.00, a lot of money for 1920, it was only going to be seen by a lot of businessmen anyway and unlikely to offend the squeamish masses out there. (The Bureau of Labor Statistics has a site on the internet that tracks how the real value of money changes over time. According to its calculator, $10 in 1920 is worth nearly $120 today!)
By the way, Mr. Adams didn't stay in business long after this was published. The October 21, 1924 edition of the Appleton Post-Crescent reported that: "Ray Murtauth has purchased the plumbing business formerly conducted by L. R. Adams and will take possession at once. He at one time was in Mr. Adams' employ."