It is generally accepted that the GP, the Breguet, and the Mathey Tissot of this era were all manufactured by Mathey Tissot. The GP is, by far, the less common of the group.
Good evening, I own the white-dialed Datejust that you show in this post. I was not the original one to originally commission the work, so I'm not sure what the pattern signifies. But it is truly beautiful in person! Ed