While researching my wife's side of the family tree I came across this posting. A little more searching on the Internet came up with a genforum message where you also mention a Michael Duffy who was a Merchant Marine and who died in Finland.
Both of these together lead me to believe the people you mention are my wife's great-grandparents and above.
My wife's paternal grandmother was Dorothy Duffy, and I recently found her parents' marriage certificate in Iowa. Their names were Michael Duffy and Josephine Bernemann, and Michael's parents are listed as Anthony Duffy and Annie O'Harra (sic).
I had also made contact with someone else researching that part of the tree who mentioned (as did my mother-in-law) that Michael was in the Merchant Marine and died in Finland. (The Duffys end up back here in NY in a later census.)
I realize these messages are fairly old, but hoping a notification goes out for this response! I'd love to share notes on the family (and hopefully learn some more.)
If you can't reach me via this board, you can get me directly at my genealogy blog contact form here:http://currach.johnjtierney.com/contact/