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The significance of a chronometer rated movement is extreme accuracy. The bare movements, devoid of the date and Perpetual winding mechanism, are subject to 15 days and 15 nights of testing. During this time they are tested in 5 different positions, crown left, crown up, crown down, dial up and dial down, and at varying temperature ranging from 2oC to 32oC. Only if the movements average an accuracy of within -4/+6 seconds a day are they allowed to be endorsed as a chronometer movements.
The date feature is non-quick set, the hands must be moved through 24 hours to change the date unlike modern Rolexes that have quick set date and only required a small movement of the crown to change the date.
This movement came in two designs, the earlier models have a non-hacking movement and the latter ones a hacking one. The change to hacking from non-hacking is thought to be around 1973. However, owners seem to throw doubt on this as well. Many owners have reported that their watches are fitted with the hacking feature, but dating their watches from the serial numbers many of these were manufacture as early as 1968, a 5 year discrepancy.
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