A gage mechanism for a blood pressure measuring device or other similar apparatus includes a supported shaft member having one end in contact with an inflatable bellows. A pointer is attached at an opposite end of the shaft and a helically wound spring is attached to the shaft and a supporting structure. As the bellows inflates, the shaft is axially displaced and causes rotation due to the constraint of the helical ribbon spring, causing a corresponding angular deflection of the attached pointer relative to an indicating scale. The mechanism includes a first adjustment member for allowing the pointer to be preset to a zero or calibrated position, and a second adjustment mechanism that controls the amount of angular rotation of the shaft and pointer for a displacement of the bellows.