Thank you for your response. However, I was unable to find any reference to the
Kronprinz Wilhelm as a hospital ship. Wikipedia notes that there are no references to it in commercial records after 1923; the assumption is that it went to the ship breakers at that time or soon after, so it couldn't have served in WWII. So, it doesn't seem like it could be considered as a candidate for the first hospital ship on a stamp. I think that
Charles Roux is the primary candidate.
Nailing down "firsts" is always difficult. It depends in large part on the definition, in this case, of "hospital ship." Is a hospital ship just a ship that transports wounded soldiers? Or is such a ship an "ambulance ship"?
Charles Roux was a passenger liner before it was converted as a hospital ship.
In fact, most hospital ships started in roles that had nothing to do with medicine. In Vietnam, I was a patient on the hospital ship U.S.S.
Repose, which began life as a Type C4 class ship, the largest type of cargo ship built by the United States Maritime Commission (MARCOM) during World War II. I'm not sure that there are any hospital ships that were purpose-built as hospital ships. Even the ships U.S.N.S.
Mercy started life as an oil tanker. It seems that commerce and combat always trump medicine.
Bob Ingraham
Vancouver