Char data changing when stored in database

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C#

SQL

I am trying to store a value in the database with the following code that uses a stored procedure.

cmd.Parameters.Add("@c128", SqlDbType.NChar, 13);
cmd.Parameters["@c128"].Value = c128;

c128 is a string containing 13 characters.

The values are:

[0] 170 'ª' char
[1] 103 'g' char
[2] 87 'W'  char
[3] 86 'V'  char
[4] 106 'j' char
[5] 73 'I'  char
[6] 33 '!'  char
[7] 116 't' char
[8] 36 '$'  char
[9] 131 'ƒ' char
[10]    47 '/'  char
[11]    109 'm' char
[12]    171 '«' char

But immediately after I Execute the stored procedure, the value in the database is:

[0] 170 'ª' char
[1] 103 'g' char
[2] 87 'W'  char
[3] 86 'V'  char
[4] 106 'j' char
[5] 73 'I'  char
[6] 33 '!'  char
[7] 116 't' char
[8] 36 '$'  char
[9] 63 '?'  char
[10]    47 '/'  char
[11]    109 'm' char
[12]    171 '«' char

It replaced character 131 with a question mark.

I am clueless as to why this is happening.

Thanks,
Bryan