Pertains to the following types of external micrometers: a) External micrometers having a frame holding a micrometer spindle and nut on one side opposite a fixed anvil on the other. b) External micrometers having a frame holding a micrometer spindle and nut on one side opposite an anvil on the other, and providing for two or more alternative ranges of measurement effected by means of interchangeable or sliding anvils. c) Setting gauges for micrometers above 25 mm or 1 in.