Agreed. Looks like the original collector (a Martha Coddington) mislabeled the picture herself. Any ideas on who it is? It's driving me nuts, but the picture reminds me of one of the other ducal families in Germany.
For the record, I think the LOC's labeling of it as c. 1860-69 is off as well. With the hairstyle and dress, look more 1870s to me, but perhaps I'm wrong.