I read many things online and can confirm that the Seagate Backup Plus Slim 2TB Portable External Hard Drive (USB 3.0) aka STDR2000101 contain Samsung M9T 2TB 9.5mm Sata Drives.
I bought 2x of these external hard drives and carefully pulled the cases apart using a small prising tool and successfully harvested the drives from within.
The two drives are now in my Drobo Mini quite happily doing their thing.
Currently the drives are $119 USD with free shipping, this may seem like a moot point seeing as there are other sellers selling the Samsung M9T 2TB drives on their own for $99, but I’ve been ripped off with imitations before. Plus at the time they weren’t available in standalone form.