MadSpaniard
12
Perhaps because of the beats per hour.
Hello, and interesting question.
I think the Seiko Shippo enamel models like you posted have the 6R15 movement, which I believe beats at 21,600bph. That means 360 beats per minute and therefore 6 beats per second. Maybe the markers are 1/6th of a second to have the second hand jump at each beat to those 1/6th markers?
I don’t know for sure, but that’s the only explanation I can think of…hope that helps for whatever it’s worth, cheers!