Rolex Tru-Beat 6558 / 6556

The Rolex Tru-Beat collection, a curious and now highly coveted chapter in Rolex’s history, is primarily known for its distinctive “dead-beat” seconds complication. While the chronometer-certified Reference 6556 often takes center stage in discussions of this horological anomaly, its sibling, the Reference 6558, offers an equally fascinating, if slightly more understated, narrative. The Rolex Tru-Beat 6558 represents the non-chronometer version of this unique timepiece, sharing the innovative Caliber 1040 movement but differing in its dial markings and, occasionally, in subtle aesthetic details.  

Produced during the same innovative 1950s era as the 6556, the Reference 6558 was also intended primarily for medical professionals who could benefit from the clear, once-per-second tick of the seconds hand for tasks like measuring a patient’s pulse. Its story is intertwined with that of the 6556, sharing its initial commercial struggles and subsequent rise to cult collector status due to its rarity and the unique nature of its movement. This report will delve into the specific characteristics, variations, and significance of the Rolex Tru-Beat Reference 6558, distinguishing it from its chronometer-certified counterpart and highlighting its own unique place in vintage Rolex lore.  

2. Historical Context and Production of the Reference 6558

The Rolex Tru-Beat Reference 6558 emerged in the mid-to-late 1950s, a period when Rolex was heavily focused on developing specialized tool watches. Like the Ref. 6556, the 6558 was designed with the Caliber 1040, a movement modified from the Caliber 1030 to incorporate the dead-beat seconds complication.  

The production window for the Tru-Beat series was relatively short, generally spanning from around 1954 to the early 1960s (circa 1959-1962). Specific examples of the Reference 6558 have been dated to circa 1960 and 1961. The limited production run, a consequence of its lukewarm market reception, contributes significantly to the rarity of both Tru-Beat references today.  

3. Distinguishing Features of the Rolex Tru-Beat 6558

The Reference 6558, while sharing the core Tru-Beat functionality, possesses several key characteristics that differentiate it from the more common Reference 6556.

3.1. Non-Chronometer Status and Dial Markings

The most significant distinction of the Reference 6558 is its non-chronometer status. Unlike the 6556, which typically bears “Superlative Chronometer Officially Certified” (or the rarer “Superlative Chronometer by Official Test”) on its dial , the dial of the 6558 omits these chronometer certifications.  

Furthermore, the “Tru-Beat” model name itself is often absent from the dial of the Reference 6558. Instead, these dials might feature the simpler “Oyster Perpetual” and sometimes “Precision,” consistent with other non-chronometer Rolex models of the period. This makes visual identification reliant on other cues, such as the case reference and, if functional, the characteristic ticking seconds hand.  

3.2. Case Commonalities and Variations

Interestingly, the Reference 6558 often utilized the same cases as the Reference 6556. It has been observed that on some 6558 examples, the reference number engraved between the lugs shows the “8” stamped over a “6”, indicating that case blanks originally intended for the 6556 were repurposed for the 6558. Some auction listings also note that the inside caseback of a Ref. 6558 might be stamped “6556”. This practice suggests a pragmatic approach by Rolex to manage inventory for a model that was not a strong seller.  

4. Detailed Specifications of the Rolex Tru-Beat 6558

The Rolex Tru-Beat 6558 shares many foundational specifications with its chronometer sibling, the 6556, due to their shared Caliber 1040 movement and Oyster case architecture.

Table 1: Rolex Tru-Beat 6558 Specifications

4.1. Case and Dimensions

The Reference 6558 was housed in the classic Rolex Oyster case, predominantly crafted from stainless steel. The case diameter is generally cited as 34mm , although some sources, particularly for gold versions of the 6556 or general listings for the 6558, occasionally mention 35mm. Given the shared case origins with the 6556, the 34mm measurement appears more consistently for the steel models. The lug-to-lug distance for such 34mm Oyster cases of the era is approximately 39.5mm, with a lug width of 19mm. Case thickness is around 11.4mm to 13mm. It featured a screw-down Oyster case back and a Twinlock screw-down crown, ensuring water resistance. The crystal was acrylic (Plexiglass).  

4.2. Dial Variations

Dials on the Reference 6558 were typically silver or black. As a non-chronometer model, the dial text usually omitted “Superlative Chronometer Officially Certified” and often the “Tru-Beat” name itself. Some examples are marked “Rolex Oyster Perpetual Precision”. Applied baton or dagger-style hour markers were common.  

4.3. Hand Styles – The Arrow-Tipped Rarity

While Dauphine hour and minute hands were standard , the seconds hand on the Tru-Beat is a key feature. The most common for the Tru-Beat line was a straight red seconds hand for visibility. Blued steel seconds hands also appeared. However, a particularly rare and distinctive variation found on some Reference 6558 models is an arrow-tipped seconds hand, often in a gold tone. This arrow hand is a significant point of interest for collectors, adding another layer of rarity to this already uncommon reference.  

4.4. Movement: Caliber 1040

The Reference 6558 was powered by the same Rolex Caliber 1040 as the 6556. This automatic movement was a modification of the Caliber 1030, with an added module to create the dead-beat seconds effect, where the seconds hand “ticks” once per second. It typically featured 26 jewels and operated at 18,000 bph. The power reserve was likely similar to the Caliber 1030’s, around 36-48 hours, though specific data for the 1040 is scarce.  

5. Rarity, Collectibility, and Servicing Challenges of the 6558

The Rolex Tru-Beat Reference 6558 is considered a rare watch, arguably even more so than the Reference 6556 due to potentially lower production numbers as a non-chronometer variant. Its appeal to collectors lies in its unique dead-beat seconds complication, its connection to a specific professional use (medical), and the general scarcity of all Tru-Beat models.  

The arrow-tipped seconds hand variant of the 6558 is particularly sought after due to its distinctiveness and rarity. As with all Tru-Beats, the Caliber 1040’s dead-beat module presents significant servicing challenges. Due to the scarcity of specialized parts, many Tru-Beats, including the 6558, had their dead-beat mechanisms removed or replaced with standard Caliber 1030 components during service, causing them to lose their signature “tick”. Therefore, a Reference 6558 with its original, functioning dead-beat seconds complication intact is a prized find for collectors.  

6. Conclusion: The Tru-Beat’s Understated Sibling

The Rolex Tru-Beat Reference 6558 offers a nuanced variation within one of Rolex’s most unconventional model lines. As the non-chronometer version, it often presents with more understated dial aesthetics, yet it retains the fascinating Caliber 1040 with its dead-beat seconds complication. The shared case heritage with the 6556, sometimes evidenced by overstamped reference numbers, adds another layer to its story.

For collectors, the Reference 6558 is a rare and intriguing piece, especially examples featuring the distinct arrow-tipped seconds hand. Its value is intrinsically linked to the originality and functionality of its unique movement. The Tru-Beat 6558, like its chronometer counterpart, stands as a testament to a unique period of Rolex innovation and a reminder that even commercial “failures” can achieve significant horological appreciation over time.