Manufactured by the National Spirometer Company. Date given as 1854 but more likely from the 1890’s..
http://www.icollector.com/Automatic-Medical-Battery-Automatic-Spirometer_i9337335
Manufactured by the National Spirometer Company. Date given as 1854 but more likely from the 1890’s..
http://www.icollector.com/Automatic-Medical-Battery-Automatic-Spirometer_i9337335