Rolex ref 5075 big bubbleback versus 6104 big bubbleback

There are two periods of 36mm big Bubbleback. The 6075 is an earlier version while the 6104 is the later version. Even though both watches look similar, there are some small differences. One is using the fully concealed bubbleback movement while the other is using the semi closure bubbleback movement.

6075 vs 6104

6104 versus 6075