What's the deal with this army coat?

[Nick Komiya]

This coat is made of fieldgrey cloth identical to material for army EM M36 uniforms, but the following features prevent me from identifying it as a WW2 Wehrmacht coat.

1. Back belt with only 1 button
2. The reverse side of collar is not fieldgrey, but in the same blue green as the obverse side
3. There are no usual size and depot markings
4. Buttons are officer style

Despite being a WW2 collector, I've kept this in my collection, as it served as a cheap substitute for a rolled up EM coat attached around a tornister. I never seriously tried to identify it until now, though I had it for more than 30 years. Is this a postwar BW coat?