What codepage encodes a 'ç' as '?º' (0x3f 0xba)

Today I received a file from a customer that I have to read, but it contains strange characters. Using known names, I can guess the meaning of some characters.

For example:

Realname  | Encoded as   | sign  | hex
----------|--------------|-------|-------
Françios  | Fran?ºios    | ç     | 3f ba
André     | Andr??       | é     | 3f 3f
Hélène    | H??l?¿ne     | è     | 3f bf
etc.

• I have tried all codepages (known to .Net) to import the file, and see if they contain the words I know. But no codepage gives me satisfaction.
• Opening the file in Notepad++ thinks it is ANSI, and also shows the unwanted characters. (But it has a hex-editor plugin that is usefull).
• Other files (from the same user & zipfile) are encoded in UTF-8.

From the guy I received the files from, I cannot expect help. (Using Google Translate) he made it clear to me that he found it very hard just to create the files, and he is using software (I believe SAP) that I do not have access to.

Is there any other way I can find the encoding of the files he just send to me?