As far as I know, Cortland owns Diamondback 100%. They have the same phone number, and the same people answer for each company
The Diamondback models have changed substantially in some cases, and
some rods have simply been given a new name. It seemed like Cortland was
going to dump the brand altogether, but the addition of the Flawless would
indicate they giving it a shot.
When I spoke to the Cortland/Diamondback repair department, the guys told
me they still had plenty of sections for Diamondback Aeroflex rods. In fact,
the guys at the Cortland store had "tons" of Aeroflex rods for sale, and they
haven't made that model in years.