Claim: The union that had the most members in 1907 was Kirkintilloch and Twechar Miners' Association, which was founded in 1893, and the second union with the most members was Scottish Shale Miners and Manual Workers' Union Association, which was founded in 1896.
Evidence: The National Union of Scottish Mineworkers (NUSW) is a trade union in Scotland, founded in 1894 as the Scottish Miners Federation.