Hi overmod
More or less what they where brake repeat containers that where maned
https://www.shapeways.com/product/KSD3TCVLG/freightliner-guards-pod-kit?optionId=43756440&li=marketplace
But I won't be getting any I prefer the traditional Caboose or brake van depending on nation modeled at the time.
Strangely I have not been able to find a picture of the real experemental thing they must have been real bad to ride in, being over the last bogie (truck) in the train.
regards John