Rolex Bubbleback My favorite

The Bubbleback Story: Bubblebacks marked the introduction of the first successful self winding wrist watch movement. The name bubble back derives from the rounded caseback to accommodate the self winding movement. 

The bubble back model was introduced in 1933 and was continued well into the late 1940’s with countless variations of metal and dial configuration. Bubble backs were made in stainless steel, steel and gold, rose gold, 9K, 10K, 14K, 18K, hooded case variations, even manual wind versions in the 1930’s. 

The early models through the 1940’s featured dials with luminous indexes and luminous hands. Later in the 1950’s, the dials had generally less interesting small raised dial indexes and non luminous hands.  

Each Bubbleback is different... My favorite bubblebacks

第一代：1933-1935年，8 3/4''' Hunter早期机芯有调整槽（Didactic），方便维修调整快慢，另外刻上英/法两种语言作注释。

第二代: (1935-1941年) 8 3/4''' Hunter基本与第一代无太大区别，但少了刻印和注释。

第三代: (1941-1943年) 9 3/4''' Hunter初次采用NA机芯，称为620的9 3/4尺寸相比更大，配件也有了不同配置

第四代: (1943-1945年) 9 3/4''' Hunter盘面开始刻有法文（CHRONOMÈTRE），此天文台标准需达到五方位行走十日内，并要求测试在2-32°温差中，达到不超出0-15秒误差范围。

第五代: (1945-1946年) 9 3/4''' Hunter在转陀上刻上PERPETUAL专利技术，以此加强技术垄断。

第六代: (1946-1955年) 9 3/4''' Hunter早期除了刻字有轻微区别外，与第五代差异不大，重点是中后期出现的半封闭自动陀。

这六代机芯贯穿整个泡泡背时期，直到1955年全线停产，更换为蝴蝶陀的10系列机芯