As far as the ★ goes, i cant see it really being a trademark as such for a badge maker / Metallwarenfabrik, based alone on the impossibility of having any form of patent on a star. (or even having a simple star as a trademark) That would not be legally possible today either. More likely it is nothing more than a fancy attachment guide marker, found in many forms on small enamel badges, i.e: a line, a dot, a circle...
The Deutscher Offizier-Verein is one that i hadn't thought about, but it cant be a candidate here IMO, simply because of the actual badges that i am referring to - their purpose (political and not army) - as well as who could buy them, and how they were (supposed) to be bought.
Regarding the * as a trademark, I would bet against it also. A space filler or attachment guide is more apt to being the answer. Simple is usually the way to go. Not to say it's a definite, but surely shouldn't read more into it. I think Gregg might be onto something with suggesting the Officer's Club.
Could it be some type of ejector mark?