I always wondered about this. So it looks like this is the first one, then Gundam Weapons 2-5 follow, and after that we have the sequence that runs from 1996 to the present day, starting with the Z Gundam volume?
/s/69d60759ff/2905055-135 This page explains it better than I can. 5 and 6 were out of print and republished as Master Grade Model Gundam and Zaku, respectively. Then there's the Zeta one and the ones after.