Indicator (distance amplifying instrument) - Wikipedia
Dial Indicator with Magnetic Base and Point Precision Inspection Set, Dial Test Indicator Long Arm 0-1" Professional Gauge 0.001", Magnetic Dial Indicator Base Holder with Fine Adjustment, by NAKAO: Amazon.com: Industrial &
Dial Indicator: Construction, Types, Working Principle, Applications, Advantages, and Disadvantages [PDF] – Design | Engineering