How Many Common, Unique Letters Do *You* Think There Are?

[Rafal]

I marked here common signs from EVA alphabet:
   

I would totally ignore capital EVA letters as different things.

It gives 18 letters.
Then I could assume that these are variants of the same letter:
- i and n
- c, e, and h
- f and p

It gives 14 letters.

But this approach has limitations. You have groups of letters (ligatures???) like  cTh  which are probably single symbols