There are two things you can do to try and find the manufacturer.
First, look at the card itself - it should have a name or model number printed somewhere on it. On the Tuner chip itself there is usually a model number and revision number. Google these numbers/names to find the manufacturer, then note the model number.
Second, go to Device Manager and find the unknown device (because it has no driver it will be unknown). Right click and choose Properties. In the drop-down choose Hardware IDs. Note the 4 digit code after VEN and DEV. Then go here: PCI Vendor and Device Lists
and determine the manufacturer and model number.
Then go to the manufacturer's website and download the driver for the tuner.
You will also need to download and install the software for the card to use it as a tuner. The driver and the software provide two different functions.
Let us know what you find.