A manually settable, tamper resistant indicator device suitable for use in medical and other professions, and a method for operating the device, are disclosed. An indicia member is manually moved relative to a pointer member, in setting the indicator device to display selected indicia at a pointing area. The displayed information is locked by fixing the indicia member relative to the pointer member, using a tamper resistant locking member. A fastening device, which may be tamper resistant, is used for attaching the indicator device to an article, which may be a medical device attached to a medical patient. The indicator device may be sterilized. In a medical setting, the displayed information may include a day, a date, a usage count or a personnel identifier. In one example, the indicia member has a plurality of sliding strips, each sliding strip being mounted to the pointer member and independently movable.