Rolex ref 5031 (from 1947) big bubbleback 勞力士大泡泡背

The following references are the true Rolex Big Bubbleback series. To qualify as a Big bubbleback, the watch must be 36mm in diameter and with either the A295 or A296 movements with date function. Basing on the information I have gathered, there are 13 references of the big bubbleback and I have managed to find 5 references. The Big bubbleback is much bigger than the normal bubbleback (36mm diameter versus 32mm) and is also fatter in the thickness of movements.

Rolex 4467 ( from year 1945-1949)  caliber 745 only in solid gold,
Rolex 5030 (solid gold) 5031 5075, 6031 (Steel and gold from year 1949 - 1950) start of the bi color steel gold watches

Rolex 6075 fluted bezel, 6074 smooth bezel (from year 1950 - 1953)
Rolex 6104, 6105, 6155 (modified A296，from year 1951 - 1953) 
Rolex 6304 , 6305 (A296，from year 1953 - 1956)

This afternoon, I was fortunate as Cheong Gor’s shop was opened (his shop is often closed) plus I was also lucky enough to find the ref 5031 big bubbleback from 1947.  As this is quite a rare reference, I have decided to part away my solid gold Rolex 3372 plus cash top up for the 5031. 

The 5031 is special as it has the earlier fully sealed bubbleback movement 封鉈芯; the calendar on the dial also uses the early red display, and the calendar position is without the gold frame. In addition, It still retains its straight lugs, the only two Pre-datejust cases that still retain the horizontal end and the rolex oyster screw down winding crown, maintaining the enlarged appearance of the watch. I was told that its production period is only one year. I hope to find one ref 5075 and a 6075 or 74 soon to wrap up my quest for the Big Bubbleback

1949年是勞力士首次推出金鋼款式的ref.5031(5030為18k金殼)全自動加日曆功能腕錶, 最為特別之處是放棄最早期ref.4467(1945-49年)的外型設計,從返早年Bubbleback的外型模式. 呢隻係較早期嘅全封密式機芯外,面盤上日曆也是採用早期的紅色曰曆顯示外,日曆位置仍未釘上金框.  最喜愛是佢係唯二的Pre-datejust殼上四耳內仍保留橫端及配搭官仔把的,保持官財仔放大後的外貌. 另一隻係6031。

此外件殼也是於衆多有日曆功能的大官財中最為肥,最笨重,粗壯款式,再加上其出產期只為一年. 以標準日曆功能腕錶36mm橫度呎吋及日曆位置只有距離錶殼19mm的不尋常比例下款式供應於市場,仍採用過往4467的A.295 cal. 10 1/2L (全封密式)作為標準機芯. 可惜當年未為市場接受,於1950年由ref.6075取替後也正式印上Datejust字於面盤中!

Below photos showing Rolex 6105 versus 5031. Both watches are similar in size and thickness except that the 5031 has straight lugs. In addition, the 5031 has a full bubbleback movement while the 6105 has a semi bubbleback movement.

The Rolex 5031(right) has a straight lugs while the 6105 has a curve lugs.

The Rolex 5031 (Right) is much bigger than the normal bubbleback (center)

        Ref.#                  Production date:     Movement:
        4467                  1945 - 1949         A.295(全封密式)
        5031/5075/6031 1949 - 1950        A.295
        5030                   1949 - 1950         A.295
        6075                   1950 - 1953         A.295
        6074                   1950 - 1953         A.295
        6104                   1951 - 1953         A.296(半封密式)
        6105/6155           1951 - 1953         A.296
        6304                   1953 - 1956         A.296
        6305                   1953 - 1956         A.296
        6605                   1956 - 1959         A.296或1065(卡啦時期.前期A.296、後期cal.1065)
        6604            1956 - 1959         A.296或1065(卡啦時期.前期A.296、後期cal.1065)