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What do you look for when choosing a mechanical watch?
Many people would probably answer "design," "functionality," and "asset value." Of course, appearance and resale value are very important points, but by increasing your knowledge and understanding of the historical background of brands and models, minor changes over the years, and other such things, you will come to love watches even more and enjoy the fun of choosing one. In this column, we will provide as much knowledge as possible about mechanical watches to both beginners and advanced users, and thoroughly dissect and explain them in detail to serve as a reference for your watch selection.
This time, we will be focusing on the Rolex Submariner Ref. 16800 & Ref. 168000, so be sure to read to the end.
Second Generation Submariner Date Ref. 16800
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The "Ref. 16800", which is positioned as the second generation, was released around 1980 as the successor to the second generation Submariner Date "Ref. 1680".
From this model, the windshield has been changed from plastic to sapphire crystal, and the water resistance has been improved to 300m. In addition, it is equipped with a unidirectional rotating bezel and the movement has been upgraded to "Cal.3035" (quick change possible), making it a more modern specification.
Compared to the previous model, Ref. 1680, this model has evolved significantly in terms of both specifications and functionality, but it still boasts enduring popularity, with its charm different from current models due to its dial design that retains a vintage feel and the unique changes that occur over time.
Basic specifications
Year of manufacture: 1980-1988 Case: 40mm
Bezel: Unidirectional (aluminum insert)
Windshield: Sapphire crystal Waterproof: 300m waterproof Bracelet: Hard bracelet (93150/593)
Movement: Cal.3035
Frequency: 28,800 vibrations
①Dial
There are two main dial variations of the "Ref.16800", classified as the early matte dial and the later lacquer dial. They are easier to distinguish from the "Ref.1680" because they can be distinguished by the markings at the 6 o'clock position on the dial and the specifications of the index.
◯Matte dial (around 1980-84) 
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The first models featured a matte black dial with borderless indexes. This design inherited the characteristics of the previous model, Ref. 1680, and is still popular today because of its strong vintage feel.
The 6 o'clock position on the dial reads "SWISS - T<25" and tritium is used for the luminous paint. As a result, many of these watches show a "patina" that changes the color of the luminous material on the indexes and hands to a cream color over time, making them highly valued among collectors.
Lacquer dial (around 1984-88) 
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The dial design changed around 1984, and a glossy black lacquer dial was adopted. This dial has a metal frame added to the index, changing it into a more modern design.
The lacquer dial still has "SWISS - T<25" written at 6 o'clock, and tritium is used for the luminous paint, but many of these do not show the same aging (burning) as matte dials. Also, due to the nature of the paint used at the time, some of these dials have cracks, commonly known as "spider dials."
②Bezel
The unidirectional rotating bezel was first adopted with the "Ref.16800". The previous model, the "Ref.1680", had a bidirectional rotating bezel, which meant there was a risk that a diver would accidentally move the bezel.
The unidirectional rotating bezel was introduced to prevent accidental clockwise rotation during a dive, thereby undercounting the actual dive time – an essential feature for divers to keep track of the amount of oxygen remaining in their tanks.
③Bracelet
The bracelet is a sturdy hard bracelet, 93150/593, which comes standard with the watch. The bracelet on this model is equipped with an extension, so it can be worn over a wetsuit.
Another attractive feature of this generation of bracelet is that it is slimmer and lighter than current models, giving it a vintage feel when worn.
Submariner Date Ref. 168000
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The "Ref. 168000" was released around 1987 as the final evolution of the "Ref. 16800". The appearance is almost the same, but the biggest feature is that the case material has been changed from 316L stainless steel to 904L stainless steel. This change in material has improved corrosion resistance and evolved into a more sturdy case structure. However, the production period was short, only about three years (around 1985-88), and the number of units produced was small, so it is a model that is difficult to find in good condition today.
Basic specifications
Year of manufacture: 1985-88 Case: 40mm (904L stainless steel)
Bezel: Unidirectional (aluminum insert)
Windshield: Sapphire crystal Waterproof: 300m waterproof Bracelet: Hard bracelet (93150/593)
Movement: Cal.3035
Frequency: 28,800 vibrations
①Dial
The dial of the "Ref.168000" is basically the same as the later model (lacquer dial) of the "Ref.16800". There are no major changes to the dial design, the inscription "SWISS - T<25" is at 6 o'clock, and tritium is used for the luminous paint.
◯SWISS - T＜25 notation (1987)
The "SWISS - T<25" inscription at 6 o'clock indicates the use of tritium luminous material.
"SWISS" - indicates that the product is made in Switzerland
"T<25" → Indicates the "T" for tritium and that the radiation dose of tritium is less than 25mCi (microcuries).
The tritium luminous material from this era deteriorates over time, and some pieces turn a cream color (patina). The beautiful, evenly burnt dial is one of the points that makes it highly valued in the market. In addition, the indexes with metal frames are used, improving visibility and giving it a luxurious design.
②Bezel
The Ref.168000 is equipped with a unidirectional bezel with an aluminum insert. This is inherited from the Ref.16800 and is one of the points that further improves its functionality as a diver's watch. For a diver's watch, the unidirectional bezel is a very important function. By preventing the bezel from rotating clockwise, it is possible to prevent incorrect measurement of diving time and accurately manage the remaining amount of oxygen in the tank.
③Bracelet
The bracelet is the 93150/593. This bracelet is a robust hard bracelet type with a diver's extension, so it can be worn over a wetsuit. The flash fit is also detachable from the bracelet, maintaining the classic Submariner design of the time.
Known as "Triple Zero"
Although the "Ref.168000" is a five-digit reference generation, the model number is six digits, with the last three digits being "0", which is why it is nicknamed the "triple zero". Also, although "168000" is clearly engraved on the 6 o'clock side of the case, there are some cases where "16800" is engraved on the warranty card or back cover.
Second Generation Summary
The "Ref. 16800" and "Ref. 168000" played an important role in the evolution of the Submariner. In particular, they were the first to feature a sapphire crystal windshield and a unidirectional rotating bezel, bringing them up to specifications that are common to modern Submariners.
The matte dial "Ref. 16800" is also popular among vintage models, and those with beautiful luminous finishes are traded at high prices. On the other hand, the "Ref. 168000" was produced for a short period of time, so it tends to be a rare collector's item.
This is one of the models that is attracting a lot of attention in the vintage market, so be sure to get one that satisfies your needs.
See you later!
