That's awesome. Makes me miss the little guy.
I tried for about 2 years to dig up info on Mr. Hartmann. Had I succeeded to the extent you have, it would have taken a lot more than the DPhi!
The stars thing is still a mystery. During the turmoil of the 70s, they lost a great deal of their knowledge about esoteric history, so even the DPhis don't know. I think my assumption about what they represent is correct, but this "rule" was probably not consistently part of every chapter's esoteric instruction.
As a result, it was probably left to the jeweler and the undergrads to work it out, maybe copying the designs of older alums, maybe choosing the number at random.
I'm going with a semi-educated guess of 1854 for the badge, but of course that's based on the most optimistic interpretation. Construction alone would have made me guess 1870s.
Anyway, it's a great piece.
wptw