The Seiko 4R36 et al movements appeared sometime during mid 2011 and much excitement ensued simply for the fact that Seiko was now equipping relatively run of the mill watches with a movement capable of being handwound and hacked. Here and there on various watch fora have appeared pretty in depth posts regarding the construction of the ‘new’ 4R movements and I certainly wouldn’t attempt to replicate those here. Suffice to say, the precursor to the 4R family was the 6R15 – and this movement was intially used to power the likes of the Japanese market SARB (Spirit) series, introduced late 2005 and the now highly regarded SBDC001 ‘Sumo’ dive watch, introduced early 2007. The 6R15 was notable for the same reasons as the later 4Rs – hacking and handwinding; in addition, the 6R15 featured a Spron 510 mainspring which gave the calibre a power reserve of over 50 hours once fully wound.
What is significant is that the 6R15 was a development of the venerable 7S26, Seiko’s workhorse movement which has been powering bread and butter 5s since 1996. Thus, it wasn’t a reintroduction (as per the 4S15), it was a re-engineering of an existing, well proven calibre in order (arguably) to bring Seiko’s mid range offerings into the territory of basic ETA 2824 equipped watches. As is the way with Seiko, the 7S26 has been developed during ts lifetime, starting with the A variant (1996-2006) and progressing through the B (late 2006-2011) to the current C version (late 2011 onwards).
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