Shimokawa Watch Dissection Book 1675

Second-Generation GMT-Master Ref. 1675

A thorough explanation of the Rolex GMT-Master Ref. 1675!

The Rolex GMT-Master is a tool watch with a dual time zone display function that was developed for Pan American World Airways pilots in 1955. The second-generation model, Ref. 1675, was released in 1959 and became a best-selling model that was manufactured for over 20 years.

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Basic specifications (common to mirrors and mats)
•Production period: 1959-1979 •Case size: 40mm
•Case material: Stainless steel •Crystal: Plastic •Water resistance: 50m
• Bezel: Bidirectional rotating • Movement: Cal.1560, Cal.1570

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1. Dial

◯ Mirror (gilt) dial: circa 1959-1966

The beautiful dial features a glossy black dial with gold lettering. This is an early model of the Ref. 1675 that combines luxury and classic style, and is highly valued by collectors and is now extremely rare.

Mk0 (circa 1959) [OCC notation]
- Chronometer notation is "OCC (OFFICIALLY CERTIFIED CHRONOMETER)"
・"OYSTER-PERPETUAL" with a hyphen (fits all circle mirrors)
- The dial is rare as it has just been replaced by the Ref. 6542.

Mk1 (circa 1959-61)
The notation was changed to "SCOC (SUPERLATIVE CHRONOMETER)." The crown mark was made thinner and had a hand-drawn style (basically, there were no six-dot or underlines).
・The “O” in OFFICIALLY is in a font that resembles a circle.

Mk2 (circa 1960-64)
- A sophisticated crown mark like the current model - The “O” in “OFFICIALLY” is a thin oval - The “M” in “GMT-MASTER” has a deep valley and the “A” has a wide, flat top.

Mk3 (circa 1960-64)
-The only circle mirror dial with serifs in addition to the "ROLEX" logo.
- The model name and chronometer notation are bold and include serifs.
- Rare designs such as underlines and "6 dots" are also available.

Mk4 (circa 1963-65)
The chapter ring has been omitted, giving it a cleaner impression. The crown is classic, with the OYSTER PERPETUAL letters spaced closely together. Only "SWISS" is inscribed at the 6 o'clock position.

Mk5 (circa 1963-65)
・Characterized by bold letters with serifs ・A unique font in which the "L" and "E" in "ROLEX" jump up ・Almost even crown mark ・Double Swiss and underline dials available

Mk6 (circa 1963-67)
・Final mirror dial model ・Changed to "SWISS - T < 25" ・Dial printing has an atmosphere similar to the matte transition period

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Matte dial: circa 1967-1979

The matte black dial replaced the mirror-black dial, emphasizing visibility. The lack of shine accentuated the contrast with the white markings, further enhancing the watch's character as a tool watch.

Mk1 (circa 1967-1972) [Long E]
・The center bar of the "E" in "ROLEX" is long (long E), the same length as the horizontal bars above and below it. ・The Gothic font is well-balanced and has no serifs. ・The crown mark is slender and has long peaks.

Mk2 (circa 1972-73)
・The "ROLEX" logo is bold and soft. ・The space between the letters "OYSTER" and "PERPETUAL" is slightly wide and there are no serifs. ・The production period was short and there was little market circulation.

Mk2.5 (circa 1972-75)
・Features a handwritten crown mark ・Bold "ROLEX" logo is used, with large "L" and "E" serifs ・The "S" at the start of the first line of the chronometer notation and the "O" at the start of the second line are slightly larger

Mk3 (circa 1976-78)
The luminous indices are small and positioned inward. The crown mark is vertical and has serifs on the Oyster inscription. The chronometer and SWISS-T<25 inscriptions also have serifs. This is commonly known as a "radial dial."

Mk4 (circa 1975-79)
The crown mark is slightly longer and similar to the Mk.5, but the shape of the mouth is closer to the Mk.3. The Oyster designation has returned to a serif-less design. If the vertical line on the right side of the "M" is extended downward, it will pass through the "C."

Mk5 (circa 1977-79)
The crown mark is slightly longer and flatter than the Mk.4, with a different mouth shape. The vertical line of the "M" extends between the "C" and "H" (identification points).
・Mk.5 is further subdivided

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2. Bezel Insert
Mk.1 bezel (circa 1959-1968)
The triangle at 12 o'clock is an equilateral triangle. Small numbers are printed throughout. The initial bezel is bold, but it becomes slightly thinner in later years.

Mk.2 bezel (late 1960s - circa 1979)
The triangle at 12 o'clock is an isosceles triangle. The numbers are larger overall. The numbers are divided into three types based on their thickness: mega fat, fat, and normal. The thicker the numbers, the older the model. *Black bezels began appearing with the Mk.2 bezel.

Service insert (Mk.3) - Similar to the original insert for the Ref. 16750 and Mk.1 bezel, but the triangle is an isosceles triangle rather than an equilateral one, and the top of the number "8" is larger.

(Mk.4) Original insert for Ref.16750. Largest triangle. The circles above and below the number "8" are nearly perfect circles.

Differences can also be seen in the stainless steel part of the bezel depending on the age, with early models having deep vertical grooves, while older models with mirror dials prefer deeper grooves.
The grooves become shallower as the piece ages, but depending on how well it is polished it can be difficult to tell.

The unique charm of vintage items is that the red and blue fade over time, creating shades of pink, purple, sky blue, etc.

3. Bracelet

Rivet bracelet (7206/80): circa 1959-1971

・Jubilee bracelet (6251H/55): circa 1959 to mid-1970s

・Wound bracelet (7836/280 (380)): circa 1967 - circa 1976

Hard Breath (78360/580): circa 1976

Hard Jubilee Bracelet (62510H/550): Mid-1970s

Whether or not a bracelet's originality is preserved is also an important point in the vintage market.

4. Crown Guard: Pointed Crown Guard (PCG)
The first early model GMT Master with a crown guard that tapers towards the crown

Unlike the later and earlier models, the tip is sharp.

The PCG is a rare detail found only on early models, both early and late models.

Round Crown Guard (RCG)
Early model: Flat crown guard on top (front of the watch)

Although there are differences in thickness between later models, this is a standard crown guard that is also used in current models.

summary

The Rolex GMT-Master Ref. 1675 has changed its appearance over time, from mirror (gilt) to matte.
The gloss and solidity of the mirror period, and the practicality and classic atmosphere of the matte period. Both have their own charms, and each dial has its own subtle differences and background.

In particular, the Long E (Mk1), the Mk0 with OCC markings, and rare underline specifications have been highly acclaimed in the market, and those remaining in their original condition are becoming increasingly rare every year.

Just like the Ref.1680 red and white subs, the world of the Ref.1675 is a model filled with deep, profound charm. We hope you will take note of the stories embedded in each watch.

See you again in the next model explanation!