I'm thinking that these photos were related to some sort of experiment to see if automobile boxcars could be used in this kind of service. Flat cars would have been in high demand for all sorts of war-related cargos, but with the domestic automobile industry largely shut down for production of other war goods, there would have been a large fleet of automobile cars available for other uses. If light tanks could be accommodated, that would have been very useful – and as a bonus, their movements would have been less viewable.

Of course, if the floorboards on the automobile cars couldn't take the load... but I'll bet they could accommodate armoured cars, and likely trucks of the day.

Ian Cranstone
Osgoode, Ontario, Canada
lamontc@...