I already checked BP1012 and here are the key fields I have to populate:
BP1012 PARTNER Business Partner Number FOB PARTNR
BP1012 TIMESTAMP Time Stamp; Obsolete ??
BP1012 DIFTVAL Differentiation Criterion ??
BP1012 DATE_TO Valid-to Date for Rating ??
BP1012 GRADE_METHOD Rating Procedure ??
No other fields provided by SAP fits in these 4 remaining fields...