I believe that this is down to Bill Edwards (Carnival Encyclopedia) who many years ago, "invented" a firm called Davison. It was a case of Chinese whispers (he got a letter from someone who mentioned Davidson and he then mispelled it, and so on and so on).
To cut a very, very long story short - there is no evidence that Davidson (or Davison) made Carnival Glass.
There's a mountain of absolute rubbish in books and websites about Carnival. Much of it possibly partially accounts for my blood pressure problems. I couldn't even begin to start correcting the mistakes in some of the books, there are so many. One thing that especially irks me is when I have done lots of research and I then see the conclusion/result of all my work credited to someone else!