In fact, it has the 39mm Oystersteel monobloc middle-case of the OP essentially, which appears a little more curvaceous than the flat, trapezoid profile of the 40mm Oystersteel Submariner. The bezel of the replica rolex watches Explorer I is different on each: The OP has a domed, high-polish bezel, while the Explorer I has what Rolex calls a "Smooth" bezel. It has a flat surface instead of the convex bezel of the OP, with nicely polished.