I believe that every watch collector and every watch enthusiast is fond of watch out of their own reason. And Rolex would definitely be the most popular choice no matter for the purpose of joy, collection or investment. When it comes to why Rolex is so popular, we have to talk about the Oyster Perpetual, which developed by the Rolex founder hans wilsdorf.
1. The birth of the Oyster automatic watch
Rolex started to develope Oyster waterproof manual winding watch in 1920s and it became more and more popular. But because it was the manual winding watch, the users would forget to screw back the crown after finished winding and that leads to many watches broken because of the water seepage. A lot of customers complained about this porblem, so Mr. Wilsdorf wanted to develope a self-winding watch to avoid this problem. But because the patent right of the automatic watch technics was owned by the Harwood factory in 1920s, so Rolex has to produce the automatic watch with whole new concept based on the old manual winding watch.
Harwood factory announced to finish the business because of the bad management. Rolex learned the lesson from Harhood automatic watch.(the Harwood automatic watch was reject by customers and repair shops) So Rolex not only adopted the basic 360 degree automatic winding rotro, but also engraved the movement decomposition method on the movement in English and French to avoid the complaint of the repair shop. But the automatic movement is thicker than normal movement, so the general flat case back is not fittable, then Rolex developed the sepcial Bubbleback case back for this automatic movement. That's how this name of Bubbleback come from.
Today's Oyster Pertual is no longer the Bubbleback.The true Bubbleback was produced from 1933 to 1955.
Rolex made 6 reforms of the Bubbleback between the 1930s and 1950s, and that made Rolex became the first Chronometer watch in this world.
The first generation (1933-1935) 8 3/4'''Hunter:
we can find that there is a groove in this movement, that was to ficilitate the repair shop that they can adjust time. And every part of the movement was clearly engraved with the name in English and French.
The second generation (1935-1941) 8 3/4''' Hunter:
The second generation is not too different with the first generation, just without the groove and the parts decomposition mathod.
The third generation (1941-1943) 9 3/4''' Hunter:
Firstly adopted the NA movement. The 9 3/4 Hunter of the 620 is bigger than the former 8 3/4, and the precision is higher. The new movement has Mircometer Regulator.
The forth generation (1943-1945) 9 3/4''' Hunter:
Started to engrave the mark of "Chronometer" in French, not in English. If the watch is able to continuesly working for 10 day on 5 different positions with the deviation is under 15s and under the temperature difference of 2℃ to 32℃ with the the deviation is under ±14s.
The fifth generation (1945-1946)9 3/4''' Hunter:
The rotor of the reformed movement was engraved with "Rolex Perprtual" mark. The fifth generation even derived the 7 3/4''' Hunter cal. 420, also called PA, installed in the wamen's bubble back.
The sixth generation (1946-1955) 9 3/4''' Hunter
The double angle slope movement was produced in 1946, it was also the last generation of the bubbleback. The diameter is big but the rotor was thinner to 1mm, so it was called Semi Bubbleback. And all the six bb movement generations were ended produced in 1955.
This pic is the early sixth movement, still using the sealing rotor automatic movement.
These pics are the later sixth generation movements, has became the half sealing rotor design.
2. The sizes of the bubbleback
Generally, we can divided the bubbleback into four types: Small Round bubbleback28mm, Round end bubbleback30-32mm, Semi- Bubbleback 34mm and Big bubbleback 36mm. And the movements are generally using the full sealing or half sealing rotor.
Case: all-steel, gold plated steel case back, full gold filled, gold filled steel, gold steel, full gold 9k/10k/14kand 18k(gold or rose gold)
Bezel: Smooth, engine turned/ marked/graduated/thin milled
Dial: Sweep Seconds or Subsidiary Seconds
Square end bubbleback 30mm-32mm
1858,1873, 2490, 2764, 2765, 2940, 3009, 3130, 3131, 3132, 3133, 3134,3333, 3353, 3372, 3458, 3693, 3696, 3725, 3795, 4875, 4919, 5011, 5015, 5050,5105, 5488, 6015, 6050, 6065 and probably others
Round end bubbleback 30mm-32mm
3794, 3801, 3796, 3885, 4024, 4984, 5048, 5173 and probably others
Semi- Bubbleback 34mm
6084, 6085, 6018, 6090, 6108, 6117, 6205, 6284, 6332, 6334 and probablyothers
Big bubbleback 36mm
4467, 5027, 5029, 5030, 5031, 6026, 6028, 6075, 6105, 6304 and probablyothers
Small Round bubbleback 26mm-27mm
2849, 3348, 3501, 3505, 3686, 3794 and probably others
Hooded bubbleback 30mm-32mm
2319, 2940, 3064, 3065, 3333, 3353, 3595, 3599, 5488, 6065, 8056 andprobably others
*Above is just part of the model number