German sixth chord
A German sixth chord is a tetrad comprising a root, major third, perfect fifth, and augmented sixth, often built on the sixth degree of the minor scale.
In meantone
In meantone, the augmented sixth represents both 125/72 and 225/128. In the historically-prevalent quarter-comma meantone it is tuned only a few cents shy of a just 7/4, and in the closely related septimal meantone it explicitly represents 7/4 as well, so the meantone German sixth chord can be considered to approximate both 4:5:6:7 and 128:160:192:225.
In just intonation
Because the German sixth chord is often built on the sixth degree of a minor scale, the 128:160:192:225 found on the ♭VI of the duodene is a good candidate for its interpretation in the 5-limit.