From the looks of things I'd say the two bags, are actually one bag: the bottom I believe attaches to the top half via a zip that goes all the way around.
Found this Double Payload Duffel. o-review.com/database_detail_colorway.php?ID=145&table_name=bags
I saw that one sell, it was a great price. That’s the same bag I have for travel. It’s definitely my favorite. @Yeti there was a black one on eBay a few weeks ago and there’s also a grey one.