Benjamin, here is the photo you saw.
The coach is a Swedish elderly 3-footer (35 inch gauge) that is to be transported to a workshop at a 42 inch network for rebuild.
Both NG networks newly taken over by the Swedish State Railways at the time.
In Kristianstad south-east Sweden, circa 1950.
https://digitaltmuseum.org/021018140765/statens-jarnvagar-sj-w3t-4003-anglok-tva-overforingsvagnar-med-sparviddenTo comment on the original question in this thread. Transporters, i.e. very low (about 2 ft high) 4 or 6 axle, very sturdy cars with SG rails on top. Or transporter bogies, i.e. short bogies with a cradle on top for the SG axle, were very common on European NG networks. Not only in wartime but all throu the 19-hundreds and up to modern times, probably they are still in use somewhere. They were used on all gauges down to 29.5 inch (750 mm), but I have never seen anything like it on narrower gauges than that. Might be more than a challenge to run them on 2 ft gauge...
The photo in Earl's post is probably on meter gauge.
The stability is of course an issue. When transporters were introduced on a NG network, the super elevation of the track in curves had often to be reduced. I remember a case in the 1970-ties on the network north-east of Stockholm when a few SG cars fell of the transporters and the driver did not notice. The train arrived a the end station with a few empty transporters in the middle of the train.