A77-year-old retired school superintendent comes to the office with a report of unsteady hands. he says that for the past 6 months when his hands are resting in his lap they shake uncontrollably. he says that when he holds them out in front of his body or uses his hands, the shaking improves. he also complains of some difficulty getting up out of his chair and walking around. he denies any recent illnesses or injuries. his past medical history is significant for high blood pressure and coronary artery disease, requiring a stent in the past. he has been married for more than 50 years and has five children and 12 grandchildren. he denies any tobacco, alcohol, or drug use. his mother died of a stroke in her 70s and his father died of a heart attack in his 60s. he has a younger sister with arthritis. his children are all essentially healthy. examination reveals a fine pill-rolling tremour of his left hand. his right shows less movement. his cranial nerve examination is normal. he has some difficulty rising from his chair, his gait is slow, and it takes him time to turn around to walk back towards the examiner. he has almost no “arm swing” with his gait. what type of tremour is most likely?