Just learned something interesting, Testament Gundam was ZGMF-X12A before it was redesignated as RGX-00 (Gaia, Abyss, and Chaos were redesignated as the RGX series after being stolen by the EAF, draw your own conclusions). Also the Astray Outframe is based on the same design with its disignation as ZGFMF-X12.

With that we now know ZGMF-X9A through ZGMF-X13A:

ZGMF-X09A Justice
ZGMF-X10A Freedom
ZGMF-X11A Regenerate Gundam
ZGMF-X12A Testament Gundam (RGX-00)
ZGMF-X13A Providence Gundam

My source is Deacon_Blues from Zeonic-Corps who is working (slowly) on translating Destiny Astray.