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--- seiko_6800 [02.12.2022 20:38] – created - external edit 127.0.0.1
+++ seiko_6800 [03.12.2022 10:09] (current) – gerdlothar
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+====== Seiko 6800 ======
+**Cal. 68A** is the first of a family of ultra-thin watch movements produced by [[Seiko]] since [[1969]]. Today these movements are reserved for the upscale [[Credor]] brand. Other closely-related members of this **6800 family** include the **6810**, **6830**, **6870**, **6890**, **6898**, and **6899**.
+===== Overview =====
+The 68 family was introduced in [[1969]] with Calibre **68A**, powering a series of ultra-thin dress watches from [[Daini Seikosha]]. The line continued with the [[1973]] introduction of **Cal. 6810**, which lasted in production for a decade. These ultra-thin watches were priced double the then-highlighted quartz models and more than four times the [[King Seiko]] and [[Lord Marvel]] lineup. By 1978, the 6810 disappeared from Seiko's catalog in favor of a line of [[Seiko 7820]]-based dress watches.
+Cal. 6810 reappeared in [[1991]] with the 110th anniversary "U.T.D." watch. This round ultra-thin watch used case number 6810-6000. Two years later, Seiko introduced a new line of ultra-thin automatic watches using this moment, and these remained in the catalog for the rest of the decade.
+Cal. 6870 appeared in [[1993]] as a [[Credor]] version of Cal. 6810. It is a high-end ultra-thin [[manual winding]] movement intended to compete with similar thin calibres from [[Piaget]], [[Frederic Piguet]], and [[Jaeger-LeCoultre]]. All of the calibres in this family run at 21,600 A/h and measure just 1.98 mm thick. Most have 22 jewels, including cap jewels on the [[escape wheel]], [[fourth wheel]], and [[third wheel]].
+In [[1996]], Seiko introduced the skeletonized Cal. 6898, a total redesign of the movement. The balance wheel was moved opposite the crown thanks to a return to the circular shape, and the bridges were redesigned. A small-seconds version of this movement, Cal. 6898, appeared in 2005 and a two-handed version, Cal. 6890, in 2009.
+Cal. 6830, introduced in [[2016]], is a [[tourbillon]] version of Cal. 6800. It was used in the rare [[Credor]] Masterpiece series, model GBCC999, GBCC997, and GBCC996. Seiko claims that it is the world's smallest tourbillon in terms of volume, measuring just 1.98 mm thick apart from the open heart tourbillon, which measures 3.98 mm including the carriage and 25.6 mm diameter.
+The Calibre 68 family is assembled at Seiko's [[Shizukuishi Watch Studio]] in Morioka, Iwate prefecture, Japan, along with other high-end Seiko movements. It is one of Seiko's longest-running movement families.
+===== Technical Notes =====
+Calibre 6810 and 6870 are roughly [[tonneau]]-shaped, measuring 19.7 mm by 16.9 mm and just 1.9 mm thick, making it one of the thinnest watch movements ever produced. By this measure, it is even thinner than the famous [[Piaget 9P]] movement of the same era. However, this measurement does not include the [[cannon pinion]] and [[hour wheel]], so the true thickness is somewhat greater. Complete watches of just 4.4 mm were produced using this calibre, remaining some of the thinnest mechanical watches ever produced. These watches typically have a sealed case back, requiring access through the crystal and face. The face is held against the bezel with a spring rather than being screwed to the movement as is typical, so access to the movement requires removal of the hands and face.
+The 6800 family uses the classical 17-jewel arrangement, with 5 extra diafix cap jewels to reduce friction. Additionally, four more jewels (not included in the official count) are arranged on the plate under the barrel. These act as a glide for the mainspring which is exposed to the base plate thanks to an open-sided barrel. This novel arrangement is just one clever trick to reduce thickness.
+The [[pallet fork]] features a dog-leg bend, allowing the [[escape wheel]] to sit lower than the [[roller jewel]]. This also reduces thickness while still allowing a reasonably-sized [[balance wheel]]. The [[balance]] was also optimized, with a glued staff and integrated roller jewel to reduce thickness. It uses finely drilled holes for adjustment rather than screws of an adjuster, and the balance stud carrier is sunk into the balance cock itself rather than attached to it.
+===== Watches =====
+The Seiko 6800 family was used in just a few watch models
+  * 6800
+    * 6800-6000 (round)
+  * 6810
+    * 6810-3070 (tonneau)
+    * 6810-0010 (wide lug)
+    * 6810-0080 (tapered lug)
+    * 6810-0060 (round)
+    * 6810-3100 (tonneau)
+    * 6810-6000 (110th Anniversary SCQL002)
+    * 6810-8000 (1990's SCVL001 SCVL002)
+===== Variants =====
+^Movement ^Winding ^Hands ^Date ^Subdial ^Jewels ^Finish ^
+|68A |Manual |Hour, minute |None |None |? | |
+|6810 |:::|:::|:::|:::|22 |Tokyo stripes, rhodium plated |
+|6830 |:::|:::|:::|:::|22 | |
+|6870, 6890 |:::|:::|:::|:::|22 | |
+|6899 |:::|:::|:::|:::|26 |Tokyo stripes, gold or rhodium plated, skeletonized |
+|6898 |:::|:::|:::|[[small_seconds|Small seconds]] |:::|Tokyo stripes, gold plated, voluted ratchet wheel |
+===== External links =====
+  * [[https://reference.grail-watch.com/family/seiko-68/|Seiko 68 Family]]
+  * [[http://www.thewatchsite.com/21-japanese-watch-discussion-forum/41538-seiko-caliber-6810-thin-within.html|The Seiko caliber 6810: the thin within]]
+  * [[http://people.timezone.com/library/cjrml/cjrml0024|Four Hundred Years After, Part II, The Legacy of Seikosha]]
+  * [[http://www.seiko-watch.co.jp/resource/pdf/manual/6810.PDF|Seiko 6810 Manual]]
+  * [[http://www.seiko-watch.co.jp/resource/pdf/manual/BGMCE.pdf|Seiko Credor 6870, 6890, 6898, 6899 Manual]]
+<WRAP ud ud_mov>
+**Description:**
+  * [[Manual winding]] ultra-thin movement
+**Functions:**
+  * Hours, minutes
+  * [[Small seconds]]
+**Data:**
+  * 21, 22, or 26 [[jewels]]
+  * 21,600 A/h
+**Production period:**
+  * Since [[1969]]
+</WRAP>
+{{tag>Movements Ultra-thin_movements Manual_winding_movements Seiko_calibres Daini_Seikosha_calibres}}