 However, in the long run, this improved the union's financial position and strength, and by 1877 it had 6,749 members.By 1900 the union had 38,830 members, but roughly half were based in London.In 1921 the OBS merged with the Manchester Unity of Operative Bricklayers' Society and the Operative Society of Masons, Quarrymen and Allied Trades of England and Wales to form the Amalgamated Union of Building Trade Workers (AUBTW).