One doesn't have to "suspect" or "guess." Numbers can tell you exactly what that character is.

Formulas in example shown in screenshot:
In B2, filled down:
=CODE(MID(A2,3,1))
In C2, filled down:
=CHAR(B2)
In D2, filled down:
=FIND(C2,A2,1)
And for finding the double-quotes:

Formulas in example shown in screenshot:
In B2, filled down:
=CODE(MID(A2,LEN(A2),1))
In C2, filled down:
=CHAR(B2)
In D2, filled down:
=FIND(C2,A2,1)
If you are searching for a straight double-quote and want to put that directly into a formula you need to "escape" with extra " , like this:
=FIND("""",A2,1)
And to find a curly double-quote, you can do this:
=FIND(CHAR(8221),A3,1)
To me it seems as if FIND is working fine in Numbers.
SG