FWIW, I have a Swiss made Hohner Primaton IV tuned in C#D. The basses are weird and wonderful and not particularly useful for playing music from the British Isles. All the chord are major except for Bb minor.

Push Pull Push Pull
D    A    G# F#
C#   G#    F   Bb minor

I don't know where this layout came from. Melnet has a more useful layout titled traditional here
http://forum.melodeon.net/files/site/CD21tradbass.gif
and a modern one here

http://forum.melodeon.net/files/site/CD21modernbass.gif