Now part of the Swiss Swatch Group, Certina have been around since 1888 and you can read about their history on the Certina website.

As far as electric and electronic watches are concerned, they produced the Certina Chronolympic C-Tronic tuning fork watch in the early 1970s; this used the same ESA 9210 as the more common Omega Speedsonic.

But they also produced the strange watch below, the Certina Biostar Electronic. It employes the ESA 9156 transistorised balance wheel movement...the only watch to use this movement. The 9156 is essentially the same as the very common 9154 but has some added complications for the biorhythms discs.

Biorhythms were "big" in the 1970s and this watch allowed you to look at you Intellect, Emotion and Fitness levels for the current day. To enable it to do this, when you bought the watch, it was set up with your birth date. I've included a couple of links below the photo thumbnails where you can see what your biorhythm levels are today.

The sequence of photos below show the movement anb watch being re-assembled after a service etc:

The ESA 9156 looks like the very common 9154 from the balance side.	Markings on the plate indicate this is an ESA 9156.	The ESA 9156 from the dial side looks a little different compared to the 9154. There are no standard calendar wheels but instead a long steel arm with a multi-layered cog on it.	Let's start putting the biorhythms disc on. First, Red for Intellect	Second disc : Blue for Emotion.	Third disc : Green for Fitness!
Fourth disc : Day of the Week!	Dial and hands back on	Cased...but not yet set up.	Cased...but not yet set up.	After purchase, watchmaker would mark the new owner's birth date on the inside of the case back....	...and then use this lever to dis-engage the discs so that each one could be rotate into the correct position based on the birth date.

After purchase, the watchmaker would disengaged the discs, and then rotate each wheel, through the window in the dial, using a couple of special rubber-tip tools. It is described in German here. And you would set the wheels based on your birth date...and, with the wonders on the Internet, you can view what they should be here.