Solution
The serial number of the device is not part of the IVI C attributes such as the manufacturer or model number, thus it cannot be accessed the same way as these other properties. In the following document you can see a complete list of the IVI C attributes which are accessible via the IVI class driver: IVI C Inherent Capabilities Specification.
As a workaround, depending on the type of instrument you should be able to get the serial number of the device by using VISA commands and getting the instrument query response string by performing an *IDN? query.