A Hutchinson-style spirometer from Stoelting, a manufacturer and distributor of school supplies.  Identical, except for the nameplate, to spirometers manufactured by the Naragansett Machine Company of RI between 1900 and 1920, Stoelting sold these spirometers from around 1920 to 1940.  At guess, this one is from around 1920. Found on the Dr. Nicholas and Dorothy Cummings Center for the History of Psychology website.