 Complete the following phrase:  During the culmination in 1923 of the Hyperinflation crisis Urbig served as chairman of the Currency Committee of the Central Association of German Banks and Bank Businesses. At the same time he was a board member at the , the Berlin-based national bank set up that year to deal with the currency crisis. He was centrally involved in the introduction, in November 1923, of the German Rentenmark, a new currency which would indeed prove more stable than the old. He had been invited to accept the position of National Currency Commissioner, but his response that his appointment should involve both repudiation of the burdensome reparations imposed at Versailles and the selective unwinding of the excessively progressive social reforms introduced since 