You can check T1 Pro's serial number from bike frame, App and central display.

Bike Frame

A QR code sticker is located next to the Bluetooth speaker (see picture below).

Scan the QR code to get the SN.

If the QR code is blurry or cannot be scanned, you can also check the printed SN on the front of the bike (see picture).

App

Open the app and go to Settings. The SN will be displayed on the page.

Central display

Go to Settings > About. The SN will be shown there.

Note: This way is available only with firmware version 2.3.1 or later.