I bought a used Sinn U1 SDR on the used watch forum. It came with full box and warranty card. When I called Sinn to check, the cs staff told me that the serial number was not in the system. The sales point column on the warranty card indicated Sinn. The seller did inform me that he bought it direct from the factory. Should I be worried that it is a counterfeit? Thank you so much for your help and looking forward to your replies!