That holder is one of their older ones & is no longer made. The lettering style gives it away too. It's a CA size for their SDN40CA tool posts. The P/N for that holder would be D40CA-20C. It would have had another head on the other end. I believe it uses TNMG inserts also like their other style.
There's another #20 holder by Dorian that has the same adjustable head on one end only & does not have the dovetails on both sides like yours, just one side. That one is #20R & is also discontinued.
Aloris still makes these adjustable angle holders, they are #20, 22, & 30. Dorian currently still makes a double ended tool holder but it does not have adjustable heads, it's #12C.