So it had apparently turned out that...
Remember the Flying Hamburger (or well, a better translation, Hamburg Flyer) I wrote about on this blog a while ago? The good ol' SVT 137 high speed articulated diesel multiple units from the Deutsche Reichsbahn-Gesellschaft (German Imperial Railway) era?
The trainset had also been used for an international service called the, Berolina, introduced in 1959 between Berlin and Warsaw. They weren't replaced by locomotive-hauled trains until the 1970s. Given the trainset was designed in the 1930s, that was quite the life it had.
Anyway, I found some more old footages of the trainset on YouTube. The second video on this page is a documentary on how the SVT 137 was made in the factory. It's in German but it's quite entertaining to watch.