A spool (12), for supporting a fiber optic coil (14) and a shield (118) surrounding the spool and fiber optic coil, includes a centrally placed, bolt-receiving opening (29). The shield includes a lower shield portion (20), which supports the spool and the fiber optic coil, and an upper shield portion (118). The upper and lower shield portions are arranged to interfit with each other at an interface (121). The upper shield portion has a centrally placed fastener-receiving opening (124) which is alignable with the centrally placed, bolt-receiving opening of the spool. A bolt (156) has a head (156a), a shank (156b) and a threaded end (156c, 156d). The bolt head is engageable with the spool through intermediary structure (48). The shank is insertable through the centrally placed, bolt-receiving opening (29) and the lower shield opening (26), for radially centering the assembly and its components. The threaded end is disposed to engage a threaded opening (68) in a gyroscope assembly support (66). A threaded, centrally placed opening (156e) is located in the bolt head. A screw (164) is couplable with the upper shield portion and screwable into the bolt head threaded opening for securing the upper shield portion both to the lower shield portion and to the bolt.