There is no command available on SteelHead CLI/SHELL to find NIC card serial number, however, you can find the NIC part number/ID (which can be used to raise an RMA/order a part) using the below command
The only way to find the serial is to physically inspect the NIC card. If the fiber card was built with the unit (included in the order of SH), we can find the serial from purchase order (PO).