The 'T' in S25FL256SAGBHIT00 indicates that an enhanced security measure has been employed. The One-Time Programmable (OTP) Area has been locked, at the request of the actual end-customer. Whether or not the OTP area actually contains a special code, serial number, or password key cannot be determined, as this proprietary information is exclusive only to the end customer. Since the OTP area is locked, it is a special customer request. Therefore, the actual datasheet will not detail the 'T' option.