"Sovereign" seems to be one of those words you can attach to almost anything in order to make it sound as if it reigns supreme. My Jaguar XJ40, for instance, is a pretty standard model compared to the slightly better-appointed Vanden Plas series, but at the rear it is badged "Sovereign." In this case, I think Zenith may have very well "borrowed" the title from DuMont. Of course, they may been set on the name all along and simply didn't
mind if people made that association.
I have to admit it was really a surprise for me when I first discovered that they had 27'' televisions as early as 1952. When I first picked up my '53 Zenith, I figured that the 17'' CRT was a standard in the industry at that point. But, actually it looks like Zenith was pushing more 21'' and 24'' models that year than anything else.