Cepasaccus wroteIn “Agatha Christie’s Poroit”, S10E1, “The Mystery of the Blue Train” is a portable strong box with combination lock. It is used as a storage for an expensive diamond on a railway trip. As expected that diamond is stolen nonetheless. Sorry, don’t have a good photo and the illegal copies on youtube are really bad.
I could not resist checking our Poirot collection. Not great images, but here they are. First on the rail platform, second being dragged down the corridor:

Later, two images of the box being opened:

The dial looks Sargent & Greenleaf-ish. This would be in character, the owner is American. I can’t say whether that particular dial and ring are proper for the time but the index mark seems poorly aligned with the box. The story’s basic plot was in a 1923 short story which was later expanded as a full-length novel in 1928. But the TV series consistently was set in 1936 so that’s the year that counts.
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