Hello,
I've seen this interesting discussion and I can add that this breast star of the Black Eagle enriched with the Garter, is a copy or, better, a fake.
It starts from a copy of the Prussian order, made by Rothe & Neffe, Vienna, then fitted with a Garter, coming from one of the Blass-connected manufacturers; changed, "German"-style pin and, as a final touch, the "Godet" escutcheon.
A work depicting the production of Mr. Blass, could be quite useful, because it seems that his masterpieces are now more often appearing again on the market. A good guide though, are the catalogues of the Munich-based auction house, ruled by the late gentleman from Hamburg.
We can prepare a lavishly illustrated book on Blass's fakes (and I'd love to have a copy of it!), but never forget that it will help us about THOSE fakes only. Let's never forget that the forgerer's workshop is never closed...
In my opinion, the study of originals is the best way to avoid fakes.
All the best,
E.L.