To search using the European Classification system, which is usually just called ECLA, use the ECLA field code.

Note: It is still possible to search in AcclaimIP using the ECLA field codes.  However, in 2013, the ECLA codes were replaced with the newer Cooperative Patent Classification (CPC) system.  So EP documents are no longer published with ECLA Codes.  In other words, use the CPC field code instead!