I still haven't figured out which one I have. To be honest, stereo stuff is kind of low on my list. I just installed dampers/springs and im getting those dialed in and then I also have a few parts on the shelf waiting to get installed. I also am getting parts together for more power so I have a lot going on with the build. What is an easy way to find out?
Just compare photos online. Google RCD 310 and RCD 510, they are very easy to tell apart. If you have the 310, you'll never get great sound until you replace it.