**This is not just rare watch it is also i very unique!** **For people who want to know if they are having a good day or a bad day :)** In 1965, Certina launched the Biostar. It was the first wristwatch that allowed you to read your biorhythm. . All Biostar models must first be adjusted to the date of birth of their owner. To do this, you need to open the watch and synchronize the cycle discs using the setting values. MAnual for this can be found online. This certina Biostar Electronic ref 7501 001 is made from 1971 - 1974. Inside is ESA 9154. It works nice as need to. if somebody realy wish to use biorhythm feature, it need to set it up. Condition is very good, case have nice factory brushing and I am sure it isnt polished. there are normal micro scratches on plexyglass. there are name and date from previouse owner. Bracelet is genuine and it is for 17.5cm wrist size.. Pictures: [https://imgur.com/a/lIvfJaZ](https://imgur.com/a/lIvfJaZ) Timestamp: [https://i.imgur.com/Uh2ui6F.jpeg](https://i.imgur.com/Uh2ui6F.jpeg) Price: **750$** paypal (FF or G&S +5%), REvolut or Wise shipment included in price, worldwide (from EU ) The watches I sell are from my personal collection, I am a collector and a fan of watches, I often renew my collection by buying and exchanging watches with other collectors around the world.