Dear Gernot,
The "Prins Hendrik" is a good guess for the unknown steamboat. It's also possible that it is the "Rotterdam". Both ships are almost identical. I have a good picture of the ship, but I'm not (yet) able to attatch it to my post, sorry. I'm affraid a bit of doubt is necessary.
The "Rotterdam" is build by L.Smit & Zn. at Kinderdijk in Holland in 1898. L81,84x9,05m
In the '50 only 4 steamships survived after the 2nd World war. The "Hollandia", the "Willem III", the "Prins Hendrik" and the "Rotterdam".
Thread 16 is definitely the "JULIANA PRINSES DER NEDERLANDEN".
I'm searching for postcards and pictures of all the ships from the Nederlandsche Stoom-boot Reederij and the Nederlandsche Stoomboot Reederij Akkermans (the company name from 1949 onwards). Please contact me if you have ansichtkarten, prospects or other materials.
Wouter Akkermans (Netherlands)
Akkermans_wouter@hotmail.com