Spectra helmets are produced by 3 different manufacturers :

Manufacturer Type of mark Date
Gallet Round in the bomb 1992; 1993
CGF Gallet Armée Française in the side (black) 1994
CGF Gallet Armée Française in the side (white) 1995, 1997
Melco Armée Française in the side 1994; 1995
Induyco Armée Française in the side 1997; 2000

The Spectra made by MELCO has screws like the F1/S1 on the outside of the helmets to fix the liner.
The other Spectra (Gallet and Induyco) have rivets like F1/S2.

The Spectra2 (not an official name) differs by the missing of the rubber rim.