I did, eventually get to look at an orchestral score -- it was under copyright because it had been "reconstructed". It probably was the Genser you mention. Anyway, I didn't copy it because it was under copyright.
I hadn't been aware that this concerto was unfinished at Spohr's death, so I'm not sure what the reconstruction is all about, but the bottom line is that it seems there is only one edition, and it's not PD.
But thanks for the info anyway.