Rolex Oyster Perpetual 39mm VS Rolex Datejust 41mm We have written a very detailed but to the point comparison of the replica Rolex Datejust 41mm and the Rolex Datejust II. Both series have great timepieces, but there are some obvious differences that you can read about at another time in that article. Today, however, we’re going to review one of the models in the Rolex Datejust 41mm collection and compare it to the Oyster Perpetual 39mm to provide you with the key information you need to see which one is best for you. Let’s get started right away, shall we?Of the more than ninety models of the 41mm Rolex Datejust available, the model numbered 126300 Black Index Oyster is probably one of the most popular for several reasons. We will compare it to a very similar looking Rolex Oyster Perpetual 39mm 114300 Black Oyster. First of all, these are what most people would call excellent entry-level Rolex replica watches, and they make up two of Rolex’s ten most affordable stainless steel models for men. They both have a black sunburst dial, and by design, they are conservative models that can be worn both when dressed up and for casual use.Why is it called the Oyster Perpetual Motion? The patented Oyster case has been part of Rolex’s history since 1926, when a new seal was provided by screwing the bezel, case-back and winding crown to the middle case of the watch.The name Perpetual is due to the automatic winding that occurs with the movement of the wearer’s wrist. The kinetic energy of the wrist movement winds the rotor in the watch movement, thus refilling the power reserve. This in turn makes the watch run in a permanent way. Hence the word perpetual.