CardioPulmonary Instruments (CPI) Model 200. Horizontal rolling seal spirometer. Shown with a EPA-designed timer.
From: Burton RM, Kozel WM, Penley RP, Ward GH, Chapman RS. Application and evaluation of portable field instruments for measuring Forced Expiratory Volume of children and adults in environmental health surveys. Environmental Health Perspectives, 1974; 8: 123-131. Page 126.