Between 1960ies and the 1980ies almost until the end of the former Yugoslavia I have frequently traveled on the Orient Express route. I recommend to watch the Agatha Christie and James Bond movies covering this topic.
I noticed some difference between European 3-rail O gauge and 2-rail O scale models, because some are 1:43.5 (mainly in UK) and others 1:45 (more in Continental Europe). For more details read the product description in the manufacturer's catalog. Here is the official standardization paper: http://www.morop.org/de/normes/nem010_d.pdf