Lewis & Short

spĕcŭlātōrĭus, a, um, adj. [speculator], of or belonging to spies or scouts: navigia, spy-boats, vessels of observation, Caes. B. G. 4, 26; also called speculatoriae naves, Liv. 30, 10, 14; 35, 26, 9; 36, 42, 8; and caliga, worn by spies or scouts, Suet. Calig. 52.
Hence, subst.: spĕcŭlātōrĭa, ae, f.

  1. A. (Sc. navis.) A spy-boat, Liv. 22, 19, 5; 22, 36, 42.
  2. B. (Sc. caliga.) A boot worn by spies or scouts, Tert. Cor. Mil. 1.