NBLCL built the MKVIII international. I believe only 7 were completed by this company. Hulls for a further 100 were shipped to the USA and these machines were completed stateside
Neither of which are railway companies. They're manufacturers of locomotives (NBL) and rolling stock (Metro - you have the wrong name, by the way).
Really, just looking at a decent book on tanks will tell you who the main tank builders were, and then some basic research will tell you what their usual business was.
