They aren't mantic. The central depression is the wrong size (I've actually got both these bases and mantic ones, and mantic use a larger circle indent.)
They're for a range called "Space Lords" by a German company called Hobby Products.
Currently available through moonraker models.http://moonrakerminiatures.com/spacelords.htm
The two bottom left are GW styled ones (but GW weren't the only maker of slottabases even going back to the 90s.