How can I verify the authenticity of an iPhone 15 Pro Max?

You should not post the serial number or other personal info like the IMEI of your phone on a public site. We have asked the moderators to remove this.

What is the Model Number of your phone? Settings > General > About > Model Number

What happens when you enter the serial number to check coverage on your iPhone? Check Your Service and Support Coverage - Apple Support

If you're asking this question because you are considering buying a used or gray market device, don't.

The All Too Common SAD Reality of Buying … - Apple Community