





















































6 Hours
16
0
$21,500.00
Note: KSL, its service providers, and the seller receive data from this message. See our Privacy Notice and TOU for details.
A breathtaking and incredibly rare piece of horological history: the Rolex Oyster Perpetual "Tru-Beat" Reference 6556. Stamped I.56 inside the caseback with a 138,XXX case serial, this investment-grade medical professional's tool watch dates precisely to the first quarter of 1956. It comes paired on a beautiful, period-correct Swiss-made Rolex 7205 riveted Oyster stretch bracelet with 60 endlinks.
Condition: • Case & Bezel: The 34mm stainless steel Oyster case retains its iconic mid-century lines and smooth steel bezel with honest vintage wear. It shows normal fine surface scuffs and minor hairlines consistent with a 70-year-old untouched survivor. No major dings or egregious gouges. • Crystal: Equipped with a classic domed acrylic Plexiglass crystal in clear, excellent condition with minimal surface marks. • Dial: An absolute standout. It features the rare original "crosshair" layout displaying beautiful, concentric tropical patina along the outer perimeter where the original lacquer has aged naturally over the decades, leaving a stark, gorgeous vintage contrast.
Authenticity & Movement Health: Movement is the legendary, ultra-rare Rolex Caliber 1040. Because many Tru-Beats were converted to standard sweeping seconds during vintage service eras due to parts scarcity, finding an original Caliber 1040 running at this health profile is an exceptional rarity. • Matching Serials: The reference number 6556 matches perfectly between the 12 o'clock lugs and inside the caseback (I.56). The case serial 138### is cleanly visible at 6 o'clock, perfectly matching the mid-1956 production era. • Beat Rate: Timegrapher analysis confirms a flawlessly steady 18,000 VPH (2.5 Hz), exactly correct for this historic movement architecture. • Performance: Running exceptionally strong for a 1950s caliber with a remarkably clean, singular trace line. Amplitude sits healthy at 276 with a near-perfect beat error of 0.1 ms. • Health: Dialed in at a highly stable +17s/d positional rate. The movement shows zero signs of magnetism or erratic timekeeping behavior.
Specs: • Size: 34mm diameter (excluding crown) / 19mm lug width • Movement: Modified Chronometer Caliber 1040 Automatic (with deadbeat seconds complication) • Depth: Vintage standard (100m historically, but assume no modern water resistance) • Power reserve: Approx. 42 Hours • Includes: Watch and authentic Rolex 7205 rivet bracelet only.
KSL Classifieds makes it easy to buy and sell with peace of mind. Check our safety tips and quickly report anything that doesn’t look right to keep your experience smooth and secure.












6 Hours
16
0
$21,500.00
Note: KSL, its service providers, and the seller receive data from this message. See our Privacy Notice and TOU for details.
KSL Classifieds makes it easy to buy and sell with peace of mind. Check our safety tips and quickly report anything that doesn’t look right to keep your experience smooth and secure.






















































A breathtaking and incredibly rare piece of horological history: the Rolex Oyster Perpetual "Tru-Beat" Reference 6556. Stamped I.56 inside the caseback with a 138,XXX case serial, this investment-grade medical professional's tool watch dates precisely to the first quarter of 1956. It comes paired on a beautiful, period-correct Swiss-made Rolex 7205 riveted Oyster stretch bracelet with 60 endlinks.
Condition: • Case & Bezel: The 34mm stainless steel Oyster case retains its iconic mid-century lines and smooth steel bezel with honest vintage wear. It shows normal fine surface scuffs and minor hairlines consistent with a 70-year-old untouched survivor. No major dings or egregious gouges. • Crystal: Equipped with a classic domed acrylic Plexiglass crystal in clear, excellent condition with minimal surface marks. • Dial: An absolute standout. It features the rare original "crosshair" layout displaying beautiful, concentric tropical patina along the outer perimeter where the original lacquer has aged naturally over the decades, leaving a stark, gorgeous vintage contrast.
Authenticity & Movement Health: Movement is the legendary, ultra-rare Rolex Caliber 1040. Because many Tru-Beats were converted to standard sweeping seconds during vintage service eras due to parts scarcity, finding an original Caliber 1040 running at this health profile is an exceptional rarity. • Matching Serials: The reference number 6556 matches perfectly between the 12 o'clock lugs and inside the caseback (I.56). The case serial 138### is cleanly visible at 6 o'clock, perfectly matching the mid-1956 production era. • Beat Rate: Timegrapher analysis confirms a flawlessly steady 18,000 VPH (2.5 Hz), exactly correct for this historic movement architecture. • Performance: Running exceptionally strong for a 1950s caliber with a remarkably clean, singular trace line. Amplitude sits healthy at 276 with a near-perfect beat error of 0.1 ms. • Health: Dialed in at a highly stable +17s/d positional rate. The movement shows zero signs of magnetism or erratic timekeeping behavior.
Specs: • Size: 34mm diameter (excluding crown) / 19mm lug width • Movement: Modified Chronometer Caliber 1040 Automatic (with deadbeat seconds complication) • Depth: Vintage standard (100m historically, but assume no modern water resistance) • Power reserve: Approx. 42 Hours • Includes: Watch and authentic Rolex 7205 rivet bracelet only.











