How to check authenticity of Apple Watch Series 10

There is no way to know unless you can actually see and handle it. It’s the same problem as buying a used iPhone→The All Too Common SAD Reality of Buying a Used iPad/iPhone

If you have the serial number you can use this link→Apple - Support - Check Your Service and Support Coverage, but there is no guarantee that the serial number the seller provides is the real one.

Hello Gerry4444,

If you can access the Apple Watch model number, it should be one of those listed on here for the Apple Watch Series 10: Identify your Apple Watch - Apple Support. If you can access the model number, this is by far the most reliable indicator of an Apple Watch's authenticity.

Otherwise, if you are purchasing from Amazon, Best Buy, Swappa, Apple, Target, Walmart, or other large and reputable retailers known to sell Apple Products, then your purchase should be genuine.

On the other hand, if you are purchasing from Facebook Marketplace, Craigslist, etc., ask the seller for the model number.

Let me know if you need any more help or clarification.

Have a nice day!

Don't. Buy it from an authorized retailer.

The Apple Watch 10 is still relatively new. If you find one on line for significantly less the usual retail price, something is wrong.

Lawrence is right. Be VERY VERY VERY VERY cautious. If you can't see the watch and see that it is prepared for you, a new user, you very well could wind up buying a nice wrist ornament, you can't ever use.

Read the link he provided (The All Too Common Sad Reality), which should be taken seriously.