AMD uses code names to distinguish their GPUs in house and those often show up in the drivers etc. I couldn't find anything specifying the R9 (m?)275 specifically but "Tropo XTX" looks like a similar style name to the ones used in their other chips for example "Venus XTX" is the R9 m275X. Also 6820 follows their old GPU naming conventions so even though an HD 6820 didn't exist that could indicate that this mobile GPU is based on an older 6800 series desktop GPU which would also make sense. It's not concrete evidence but I think it's enough not to be worried about that.
As for lower FPS score, is that lower using the exact same settings for the test? If the settings were turned up or something then that could happen. I am not particularly familiar with glmark, I usually use Firestrike.