Hi Nic,
The general rule is that early Gen 3 models we're fitted with RDL. In 2004 a facelift incorporated the TC as well as the ASC on the GLS models. From there on the Gen 3 GLS had the electronic aids and the GLX still had the RDL.
Gen 4 maintained that format, but very early on the GLX models started getting the electronic aids as well (with RDL). The very recent GLS models now also sport the RDL.