If the ratings are issued in accordance with Directive 2006/23/EC, they are ‘grandfathered’. Thus, a licence with an STDI endorsement could be issued to applicants who fulfil the provisions of ATCO.C.035. In order to exercise the privileges of the STDI endorsement, the holder has to demonstrate compliance with ATCO.C.030(b) including demonstrated knowledge of current operational practices.
If the ratings are issued earlier than the Directive, the competent authority would need to assess the equivalence between the old (ICAO?) ratings and the current ones. In the case where the applicant has not held a licence (because there were no licences in the Member State in question), the applicant would need to provide evidence for the working experience in the ATC domain in question and related training records to the competent authority, which would need to evaluate whether the applicant fulfils the requirements of ATCO.C.035.