Check the Serial number of the laptop.
If you are talking about Surface devices, the following will be handy:
Find the serial number for your Surface device and accessories or Microsoft accessories
- Navigate to the Microsoft Devices page
- Attempt to register the device using its serial number-If Microsoft indicates the device is already linked to another account or marked as missing/stolen, that's a warning sign.
- Ask for proof of purchase (receipt, invoice, warranty card)
How to check if a laptop is stolen: a guide for IT teams
https://preyproject.com/blog/prey-labs-how-to-avoid-buying-a-stolen-laptop