The Classification data in question is displayed in view Classification and stored in structure table RMCLF.
This is the point that makes many of us struggle with properly reporting the Classification data of a material – we cannot directly report structure tables.
All classes used SAP-wide are stored in a table called KLAH (=Class Header Data). You cannot retrieve data in a single SE16 table report – you have to join the table with another one, table KSSK (=Allocation Table: Object to Class).
The link between them is field CLINT: Internal Class Number.
This is a technical ID of the class number – you cannot see it displayed but in background this is the identifier of the class data.
It will retrieve the Class Number that you can see below listed in classification data, field named Class:
For a successful search, you have to restrict the type of classes to materials only – check the type entered in the field Class Type (field RMCLF-KLART in MM03 display) as shown on above image as well, displayed as Class Type, value entered is 001 for materials.
The actual field to enter material number for your search is KSSK-OBJEK, (=Key of object to be classified). Watch out – you have to add 10 leading zeros before your material number, eg. number 40524281 will be altered to 000000000040524281.
Then choose Class number – KLAH-CLASS: this field will return the class number you assigned to your material in Classification view.
If you intend to use SE16 extracts, simply export KLAH and KSSK separately and link them by using CLINT.