Yes,the GC was the luxury version. It was buffed and clear anodized, whereas the standard DC was not. It is also often seen with recessed hex bolts. The catalogue also claims a 12g weight difference, with the GC being heavier. The weight difference might be totally in the hardware but Shimano had a similar case with their identical appearing Tourney and Dura-Ace centre-pulls. In that case,I have read that there was an alloy difference, so that's a possibility that I wouldn't rule out. While the castings appear identical, they might also be slightly beefier, which could account for extra weight. If you really want to know, you could disassemble a sample of each and do a comparison with a good weigh scale.