3 Answers

....what kind of harassment ?

Starting with the ref. 6239 in '63 the Daytona went through a period of incremental change link and experimentation for the rest of the decade. It really link wasn't until 1971 with the introduction of the ref. 6263 and 6265 that the model settled into a groove and found its footing. These two references carry the Daytona all the way through 1988 until the release link of the "Zenith" generation. For manually-wound Daytonas the 6263 and 6265 are king.

The Submariner's 904L steel case is 41mm wide and a tad over 12mm link tall slightly smaller than the Certina. And the power reserve is smaller too at 70 hours although it does feature a link paramagnetic blue Parachrom hairspring. Lastly it's water resistant to link 300 meters. That's 200 meters less than the Certina.