Do you know more about Goldin, its composition and use? And the time frame of its use? I would suspect it could be a troublesome material as it really looks quite convincing when polished.
The hexagonal shape must be quite experimental then, if not even you have come across something like it. On the other hand, they did seem to mean it, making a matching hexagonal button for it!
And also, whoever produced it, didn't position it at the very entry level, as it sports a genuine ivory face and had some remnants of genuine whalebone on it. But I guess these materials were not at all special back then.
One feature of interest I'd like to re-visit: the screw that fixes the underslide. I have often seen the use of only one screw in this position at Bubenreuth trade bows. However, the OP bow seems older. Have you (or anyone) ever seen the underslide fixed with only one screw like this on a pre WW2 bow?