How to tell whether a Seagate hard drive is single disk or multiple disks?

Yours must be a single-disk hard drive.

Seagate, the one with a groove in the upper right corner is a single disc, and the one without is not.

For Western Digital, if there are no four black circles, it is a single disc, and if there are four black circles, it is a double disc or more.

You can look at the pictures of the hard drive online and you will understand what I am talking about after looking at a few more.