EO, or Eight Ones, is an 8-bit EBCDIC character code represented as all ones (binary 1111 1111, hexadecimal FF). It is similar, but not identical, to the ASCII delete (DEL) or rubout character.
When translated from the EBCDIC character set to code pages with the C1 control code set, it is typically mapped to hexadecimal code 9F, in order to provide a unique character mapping in both directions.
References
Eight Ones Wikipedia(Text) CC BY-SA