FC means Federal Cartridge, LC means Lake City Ammunition Plant, the "05" is the year of manufacture. What you have there is military brass, probably M855 NATO 62gr green tip ball ammo. Standard military issue ammo for the M-16. Nothing wrong with it, just keep in mind that handloading mil spec brass requires the extra step of removing the primer crimp removed (with an inexpensive hand tool). Also, military brass tends to be heavier with thicker case walls to stand up to the abuse of combat conditions and to stand up to the heat and strain of feeding in automatic weapons. This means that the case will have less volume compared to commercial brass, so make sure you start your powder charge 10-12% below MAX and work up slowly, as pressures will likely be higher in mil spec brass and the max load may be below the published max load in your manual.

The only other thing I'd look for is to tumble the brass to get it clean, then sort through it to inspect the cases. Brass found on military and police ranges can be pretty beat up both from firing and from being trampled by many booted feet. Discard any cases that have large dents, broken rims, crushed necks etc... Small dents in the shoulder or body won't necessarily prevent the case from being safely reloaded after FL sizing, because the case will fireform to your chamber, but you might have a problem getting the powder charge to fit or the case may be further crushed during sizin or bullet seating.

Mike