For Research Dünkelblau Überrock-- Does anyone recognize this Litzen?

[PrussianMauser]

I recently bought an Dünkelblau Überrock with a black velvet collar of the older vintange, i.e. it has the Passanten for the shoulder boards and has non-parallel rows of buttons. The big question in my mind is the Passanten, which are definitely not Prussian considering the presence of red in the Litzen. I was thinking Württemberg or Mecklenburg, but I'm not sure. Railway, Post? (Hopefully not.)

What are your thoughts?

[PrussianMauser]

Bumping. Surely someone has some idea?

[Chip]

It's similar to the Württemberg Passanten, only Das Deutsche Heer shows the black line being on the outside and the red to the inside.

Chip