bettejean wrote “It doesn’t say ‘Royal Bonn’ which is odd …” and “I wonder if they produced ‘seconds’ that left out Royal in the stamp?”

Marks without “Royal” are not odd at all; on the contrary: assuming that they are ‘rare’ or ‘peculiar’ is odd. And those WITHOUT “Royal” are older (1875 – 1890) than those WITH “Royal” (1890 – 1920). See also Chris’ website entry on F.A: Mehlem (copy/paste, links don’t work here): https://www.porcelainmarksandmore.com/germany/northrhine/poppelsdorf-02/index.php