For the most part, the gold and steel Speedmaster Co-Axial Chronograph watches are the same, but let me just identify the differences. Of course the gold model comes in the 18k orange gold case. It also used the caliber 9301 versus 9300 movement. These are identical save for the gold rotor and bridge over the escapement. Last, the gold version of the watch is a different dial. The standard Speedmaster Co-Axial Chronograph (and remember, Omega Speedmaster watches have delicately different names, so make sure you know which ones you are talking about) has a matte black dial, while the gold version has a baked black enamel dial. The other prototype version has a ceramic dial. Look closely right over where the hour and minute hands connect in the middle and you'll see a light engraving in the dial that says "Zr02." That stands for Zirconium Dioxide - which is the principle material most industrial ceramics are made of if I understand correctly.
Sun-ray guilloche, Clous de Paris guilloche
I've seen lots of watches stamped to imitate guilloche, but this is the first time I've seen it in person. Up close, it's quite something:
Why is the Supermarine 2000 being made? To be honest I don't think it has anything to do with people needing more water resistance. It likely has more to do with Bremont's own motto which is "tested beyond endurance." That brand asserts the durability and robust nature of their watches, and with 500 meters of water resistance, the original Supermarine wasn't able to compete with some alternatives from brands such as Breitling, Rolex, etc... on paper. It is true that your basic "true" diver needs only 300 meters of water resistances, but there is a strange sort of mental assurance that higher water resistance levels provide. Bremont wanted anyone who bothered asking to know that Bremont does indeed have a silly deep going dive watch. Will there be competition between the Supermarine 500 and 2000? Probably, but it will be interesting to see what sales of both are like in a few years.