its a while since i saw this but its a Lancia armourd car at inchicore converted for rail use around 1922
http://www.britishpathe.com/video/armoured-cars-1/query/inchicore
hope that helps.
jesus...the mind boggles at this! if the wagon had a flying snail logo i'd say it could be a military train during the emergency! - fantastic pic dave=D