The 12 Bar Blues in Gb contains the chords Gb7 (I chord), Cb7 (which is the same as B7) (IV chord) and Db7 (V) chord. Below is the 12 Bar Blues starting on Gb7.
12 Bar Blues in Gb (Jazz Variation)
The Jazz variation of the 12 Bar Blues in Db adds some extra chords. The 12 Bar Blues structure remains the same, but certain chords are substituted. For example, the Gb7 chord in the fourth bar is substituted with an Dbm7 moving to an Gb7 chord.