Item no. C250 (cancel)
Type: cancel
Country: USA
Date of use: 5 March 1979
Special cancel (CTO) on cover advertising an event “Pittsburgh Conference on ANALYTICAL CHEMISTRY and Applied Spectroscopy” that was held in Cleveland (Ohio, USA). The cancel’ slogan reads: “Photography-Optics-Chemistry-Spectroscopy – Working Together”and shows the chemical formula of hydroquinone, a major component of most photographic developers for b/w materials.