Reference:116520: Difference between revisions

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The architecture matters. Cal 4130 uses a vertical-clutch chronograph coupling, where the cam-and-cam-follower or rocking-pinion arrangement of a horizontal clutch is replaced by two stacked discs that engage along their flat faces. The result is no jitter at start, no amplitude loss when the chronograph runs, and no backlash hop on the seconds hand. Paul Boutros's Hodinkee dissection (Part 3) confirmed the absence of jitter in a seven-day wear test with frequent chronograph use. The column wheel handles the start-stop-reset switching, the older and visually cleaner alternative to a cam-actuated system.

The 72-hour ~~power~~ reserve is ~~a real~~ upgrade~~, not~~ a ~~marketing flourish. Cal 4030 carried 52 to 54 hours depending on whose published spec was being read — Ross Povey's Revolution piece cites 52, Boutros's Hodinkee Part 2 cites 54~~, and ~~both stay on record. The jump to 72 hours puts~~ the 116520 ~~across an entire weekend~~ off-wrist ~~with reserve to spare. Forty-four jewels, 28,800 vph, COSC certification, and~~ a Rolex-made Parachrom blue hairspring on later production examples (Boutros documents Parachrom on a cal 4130 around 2013; WatchTime puts the introduction around 2005). The hour and minute counters share a single side of the movement — a layout simplification compared with cal 4030's split arrangement — and the mainspring can be replaced without ~~uncasing~~.

The 72-hour reserve is the practical point of cal. 4130. It is the upgrade a wearer actually feels, and it helps explain why the 116520 became the first in-house Daytona that could sit off-wrist for a weekend without drama.

For the full caliber lineage see [[Reference:Movements#cal-4130]].

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End links transition during the late 16520 era and arrive on the 116520 already as SEL — solid end links integral to the first link rather than a separable end-piece. The earlier 503 / 503B references applied to the 78360 and 78390 bracelets on the 16520, where the end link was a separate stamped piece. The 78490 carries the end link as part of the bracelet structure, which is why the 116520 sits flat against the lugs in a way the earliest 16520s do not.

The clasp is ~~the modern Oysterlock with the Easylink 5mm comfort extension — a lever-and-keeper inside the clasp body that gives a five-millimetre micro-adjustment~~ without ~~tools.~~ Easylink arrived on the 116520 around 2002 to 2003. The earliest 116520 production carried the older Oysterlock with no Easylink; mid-production examples onward carry the lever. The clasp blade carries a year code — single letter through 2010 (e.g. RS = 2010), ~~random three-character alphanumeric from 2011. SEL bracelets stamp~~ the date code ~~and crown into~~ the ~~underside of~~ the ~~end link itself, not just the clasp blade. See [[Reference:Bracelets]] for the full date-code table~~.

The clasp story is simple: early 116520s start without Easylink, later ones gain it, and the date code still belongs to the bracelet rather than the watch head.

The Daytona never adopted the Glidelock micro-extension that came to the Submariner-line clasps in 2010; Easylink is the only on-bracelet adjustment the 116520 ever offered.

@@ Line 87: / Line 87: @@
 The architecture matters. Cal 4130 uses a vertical-clutch chronograph coupling, where the cam-and-cam-follower or rocking-pinion arrangement of a horizontal clutch is replaced by two stacked discs that engage along their flat faces. The result is no jitter at start, no amplitude loss when the chronograph runs, and no backlash hop on the seconds hand. Paul Boutros's Hodinkee dissection (Part 3) confirmed the absence of jitter in a seven-day wear test with frequent chronograph use. The column wheel handles the start-stop-reset switching, the older and visually cleaner alternative to a cam-actuated system.
-The 72-hour power reserve is a real upgrade, not a marketing flourish. Cal 4030 carried 52 to 54 hours depending on whose published spec was being read — Ross Povey's Revolution piece cites 52, Boutros's Hodinkee Part 2 cites 54, and both stay on record. The jump to 72 hours puts the 116520 across an entire weekend off-wrist with reserve to spare. Forty-four jewels, 28,800 vph, COSC certification, and a Rolex-made Parachrom blue hairspring on later production examples (Boutros documents Parachrom on a cal 4130 around 2013; WatchTime puts the introduction around 2005). The hour and minute counters share a single side of the movement — a layout simplification compared with cal 4030's split arrangement — and the mainspring can be replaced without uncasing.
+The 72-hour reserve is the practical point of cal. 4130. It is the upgrade a wearer actually feels, and it helps explain why the 116520 became the first in-house Daytona that could sit off-wrist for a weekend without drama.
 For the full caliber lineage see [[Reference:Movements#cal-4130]].
@@ Line 144: / Line 144: @@
 End links transition during the late 16520 era and arrive on the 116520 already as SEL — solid end links integral to the first link rather than a separable end-piece. The earlier 503 / 503B references applied to the 78360 and 78390 bracelets on the 16520, where the end link was a separate stamped piece. The 78490 carries the end link as part of the bracelet structure, which is why the 116520 sits flat against the lugs in a way the earliest 16520s do not.
-The clasp is the modern Oysterlock with the Easylink 5mm comfort extension — a lever-and-keeper inside the clasp body that gives a five-millimetre micro-adjustment without tools. Easylink arrived on the 116520 around 2002 to 2003. The earliest 116520 production carried the older Oysterlock with no Easylink; mid-production examples onward carry the lever. The clasp blade carries a year code — single letter through 2010 (e.g. RS = 2010), random three-character alphanumeric from 2011. SEL bracelets stamp the date code and crown into the underside of the end link itself, not just the clasp blade. See [[Reference:Bracelets]] for the full date-code table.
+The clasp story is simple: early 116520s start without Easylink, later ones gain it, and the date code still belongs to the bracelet rather than the watch head.
 The Daytona never adopted the Glidelock micro-extension that came to the Submariner-line clasps in 2010; Easylink is the only on-bracelet adjustment the 116520 ever offered.