Now that you mention it, I looked that up and found the same thing.
Although I don't know which name came first, it's possible that
1. They changed the spelling from Una-Fon to Unaphone because people
mispronounced it (some people still do);
2. They changed it from Unaphone to Una-Fon to use as a trademark name.
For example, Leedy made and sold the "Vibraphone" and Deagan made and
sold the same type of instrument under the name "Vibraharp".
I don't know of any other variant spellings in the Deagan literature.
[ Thanks, Danielle. -- Robbie