During the first winter of the war, it became obvious that the 1894 Pattern Greatcoat was too light for the rigors of winter warfare. Combined with a push to standardize uniform manufacture, the German Army developed a heavier, simplified greatcoat for issue to the entire Army that was officially introduced in September 1915. The Bavarian Army officially introduced their version on April 1, 1916 with the only difference being that the collar on the Bavarian version was grey like the rest of the coat.
Below are some views of the Prussian version of the 1915 Pattern Greatcoat. The body of the greatcoat was grey (steingrau) wool with a collar of Reseda Green. In these pictures, the collar is a bit faded.
Now for the Bavarian version or 1916 Pattern Greatcoat:
Here are some more pictures of a different Bavarian Greatcoat:

Detail of Back Belt. Note that this button is the standard “Crown” button that was officially replaced the lion button.
From the above two examples, it’s obvious that the earlier Bavarian “Lion” buttons and the later universal “Crown” buttons were both utilized. Interestingly enough, neither example had the Bavarian Borte on the collar.
The 1916 Pattern Bavarian Greatcoat is an essential piece of uniform and as such, all unit members should strive to get one for themselves. At present, the only acceptable reproduction is from Schuster but be sure to consult with me first before ordering.