II – Second Phase: Self-winding Models – Reference 16520 with Zenith Caliber
Introduced in 1988 with an initial price of €2,451, this generation stayed in the catalog for 12 years until 2000, with a final listed price of €4,629. The model was completely redesigned with the introduction of an automatic movement and a sapphire crystal, ensuring 100 meters of water resistance.
The Zenith Caliber
The model is powered by caliber ref. 4030, derived from the Zenith 400 “El Primero,” which earned it the nickname **“Daytona Zenith.”** The movement was modified by Rolex to increase the power reserve from 42h to 52h, and to reduce the frequency from 36,000 to 28,800 vibrations per hour (5 Hz to 4 Hz).
The modifications included a full redesign of the movement: oscillating weight, gear profiles, hairsprings, balance wheels, bridges, etc. One notable evolution was the switch from a standard regulator to a **Microstella regulating system**.
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Caliber 4030 derived from Zenith 400 “El Primero”
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Caliber 4030 inside its case
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The Different Bezels
The tachymeter bezel is now made exclusively from **steel or precious metals**. It underwent several changes over time—referred to as **Type 1**, **Type 2**, and **Type 3**.
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Tachymeter Bezel “50 / 200” – Type 1
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Tachymeter Bezel “60 / 400” – Type 2
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Tachymeter Bezel “60 / 400” – Type 3 (1990–ca. 1998)
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- **Type 1 bezel** was found on early series from **1988 to 1989**, graduated from 50 to 200. It's one of the first produced and thus highly sought-after.
- **Type 2 bezel** was used from **1989 to 1990**, graduated 60 to 400 but includes a **225 marking**, which is absent on Type 3.
- **Type 3 bezel** (1990–2000) is also graduated from 60 to 400, but **without the 225 marking**.
On later **A and P serials**, the typography of the Type 3 bezel changes slightly—the letters in “Units” are more widely spaced. This very same bezel also appears on the **116520** reference.
Some models in **yellow gold (ref. 16518)** and **white gold (ref. 16519)**—which were sold on leather straps—feature slightly different bezel typography.
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Bezel on ref. 16518 (yellow gold, leather strap)
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Close-up of typography on the 16518
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The Dials
The dials of the Zenith-era Daytonas are particularly important to collectors. Their rarity can significantly influence the watch’s value.
A – The Floating Dial
Early 16520 series (R and L, between 1988 and 1989) briefly featured a dial where the word **“Cosmograph”** is visually separated from the line “Officially Certified.” This is known as a **“Floating Dial.”**
Some of the earliest white versions are nicknamed **“Porcelain”** due to the texture and sheen of the paint. These versions command a premium on the market.
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Floating Dial Daytona Zenith MK1 "Porcelain"
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Floating Dial Daytona Zenith MK1 "Black"
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B – The “4 Lines” Dial
Chronologically following the Floating Dial, this dial version omits the line **“Officially Certified.”**
It is known as the **“4 Lines Dial”**, produced in very small numbers—estimated less than a year in 1989 (early L series). It was made by Singer.
4 Lines Dial on a 16520, produced by Singer
C – The Inverted Six
The famous **“Inverted 6”** is a quirky dial detail where the “6” in the hour sub-dial is printed upside down—looking like a 9.
It appears on 16520 dials between 1988 and 1994 (**R, L, E, N, X, C, S** serials).
There are two types of Inverted 6 dials, distinguishable by typography: with or without serifs.
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Daytona "Inverted 6" MK3 Serif
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Daytona "Inverted 6" MK4 Sans Serif
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D – Dials from 1994 to 1998
Two main dial generations were used after the “Inverted 6,” between **1994 and 1998**. They differ mainly in how the text aligns with the subdials.
Notably, **MK6 dials** were used until stock ran out, and some were even filled with **Luminova**, before MK7 was introduced.
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Daytona MK5 Dial
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Daytona MK6 Dial
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E – The Patrizzi Patina
There is increasing demand for so-called **“Patrizzi dials”**, which fetch a significant premium among 16520 collectors.
These are black dials produced around **1993 to 1995** (serials S and W) that have developed oxidation on their subdials, turning **brown to dark brown**.
This patina was first identified by Italian collector **Osvaldo Patrizzi**, hence the name.
It’s due to the **Zappon varnish** used at the time, which reacts to environmental factors over time, creating the highly prized discoloration.
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Rolex Daytona 16520 with Patrizzi subdials, Zenith movement
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Close-up: Patrizzi effect on MK5 dial
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F – How to Identify a Service Dial on the 16520
The original dials of the 16520 featured **tritium lume** with the marking “T Swiss Made T” at 6 o’clock (1988–1998).
Tritium glows permanently but has a half-life of around 20 years—meaning most are no longer luminous today.
During servicing, Rolex often replaced original dials with **Luminova** ones, which glow after light exposure. These service dials are marked “Swiss Made” at 6 o’clock. The same logic applies to hands.
To check for originality: expose the dial to light, then place it in a dark room—if it still glows, it’s Luminova (post-1998 or service).
Note: The **U and A serials** from 1998–1999 came with original **Luminova dials**, so these are not considered replacements.
However, a mismatch like a tritium dial without inverted 6 on a 1988 case—or a Luminova dial on a 1993 serial—suggests service replacement.
Luminova dial on a 16520 from 1998–1999, or a service dial on earlier models
The Bracelets
The Zenith Daytona bracelets evolved over time, particularly the **clasp** and **end links**.
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Bracelet ref. 78360 (1988–1993)
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Bracelet ref. 78360 with end links 503
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In **1993**, Rolex updated the bracelet to ref. **78390**, featuring a Submariner-style **flip-lock clasp**.
The final versions (1999/2000) also introduced **Solid End Links (SEL)**.
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Bracelet 78390
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End links 503B
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The Oyster case came with screw-down pushers, ensuring perfect water resistance. Pusher reference: **24-P402**.
Rolex introduced the first **leather strap sport version** with ref. **16518** in 1991. The bezel’s typography on this model (and ref. 16519 in white gold) differs from steel versions—and is now echoed in modern ceramic bezels (ref. 116500).
Ref. 16518 also introduced the first **“Racing” dial with Arabic numerals**—a style that lives on in today’s gold Daytona models.
