caliper compasses
Webster's Dictionary (GCIDE)
Compasses \Com"pass*es\, n., pl. An instrument for describing circles, measuring figures, etc., consisting of two, or (rarely) more, pointed branches, or legs, usually joined at the top by a rivet on which they move. [1913 Webster]
Note: The compasses for drawing circles have adjustable pen points, pencil points, etc.; those used for measuring without adjustable points are generally called dividers. See Dividers. [1913 Webster]
Bow compasses. See Bow-compass.
Caliber compasses, Caliper compasses. See Calipers.
Proportional, Triangular, etc., compasses. See under Proportional, etc. [1913 Webster]
Calipers \Cal"i*pers\, n. pl. [Corrupted from caliber.] An instrument, usually resembling a pair of dividers or compasses with curved legs, for measuring the diameter or thickness of bodies, as of work shaped in a lathe or planer, timber, masts, shot, etc.; or the bore of firearms, tubes, etc.; -- called also caliper compasses, or caliber compasses. [1913 Webster]
Caliper square, a draughtsman's or mechanic's square, having a graduated bar and adjustable jaw or jaws. --Knight.
Vernier calipers. See Vernier. [1913 Webster]