1. Verify the authenticity of the product: the purchased giant mountain bike has no steel seal. You can verify the authenticity of the product by checking whether there is its logo on the frame or whether there is a giant trademark on the parts. You can also contact the official sales channel or giant official website to confirm whether there is no steel seal on the product.

2. Seek professional help: If you are in doubt about the authenticity of the product, consult a professional bicycle dealer or technician, you will know more about the seal of the giant mountain bike, and you can also provide product identification and verification services.