Apple Watch series 8 - mark on the back

Hello Mrs-Macca,

You'll want to use the recommendations and steps below to clean your Apple Watch:

Keep your Apple Watch clean and dry. Soaps, cleaning products, abrasive materials,* compressed air, ultrasonic cleaning, and external heat sources can cause damage and shouldn't be used with your Apple Watch. 

To clean your Apple Watch, follow these steps:

1. Turn off your Apple Watch and remove it from the charger.

2. If you have a leather band, remove it from your Apple Watch.

3. Wipe your Apple Watch clean with a nonabrasive, lint-free cloth. If necessary, lightly dampen the cloth with fresh water. If your Apple Watch has substances or debris visible in places such as the speaker ports, you can hold your Apple Watch under lightly running, warm, fresh water until it's clean. Soaps and other cleaning products shouldn’t be used.

4. Dry your Apple Watch with a nonabrasive, lint-free cloth, including the surface of the back crystal.

* Apple Watch is manufactured with extreme care and precision, while leveraging state-of-the-art technology to provide the best customer experience. To ensure the watch maintains all functionality and to keep a consistent finish across the enclosure and external components, Apple does not recommend polishing or buffing the watch with abrasives.

You can also find those steps in this resource: How to clean your Apple Watch - Apple Support

If those marks still persist, you'll want to reach out to Apple Support: Apple Support They'll be in the best position to look into your options further.

Take care.

Hello Mrs-Macca,

Since those marks still persisted after cleaning your Apple Watch, you'll want to contact Apple Support so they can look into your particular situation further: Apple Support

Take care.