The serial number (S/N) is present on a sticker on the backside of the PC module. The module itself can be found at the side of the board and is hold in place by two silver spring screws.
The screws can be loosened by hand or a screwdriver and the module can than be removed by pulling them.
A few examples of how the serial numbers can look like for the OPS modules.
In case a older model screen is used with older PC modules the steps are generally the same. The older serial numbers can start with MT01, MT06, MT10 and MT21.
A small exception is the MT21, this one has no screws but two small handholds and a orange "release" button.
Alternatively it is also possible to get the serial number via Windows on the PC itself. For this a command can be given via the command prompt. It is possible this option might be blocked for a normal user in Windows.
1. Open CMD via the Windows start menu.
2. Typ in the following command to get the serial number: wmic bios get serialnumber