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As previously posted, I just added a NOS 7549-7009 Golden Tuna from 1985 to my collection. This earlier Tuna is fitted with the Seiko 7549A 5 jeweled quartz movement. My SBBN007 and SBBN013 Tuna's being fitted with the Seiko 7c46 7 jeweled quartz movement call for a SR43SW battery which Seiko gives a five year replacement interval. The 7549A movement was listed with a three year battery replacement interval, but the case back does not list the battery it requires. My question is: does the 7549A movement call for the current SR43SW battery or a different battery and does it still have a three year replacement interval, perhaps due to a higher friction coefficient in the five jeweled movement, or has it been increased to five years due to newer battery technology?
 
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