This is an abbreviation for a unit being available to all tracked Inner Sphere Clans. If searching on the Units Tab, you must include both the faction and their general list in order to see all units available to that faction.
Clan Invasion: Diamond Shark, Ghost Bear, Jade Falcon, Nova Cat, Smoke Jaguar, Steel Viper, Wolf, Wolf-in-Exile.
Civil War: Diamond Shark, Ghost Bear, Hell's Horses, Jade Falcon, Nova Cat, Wolf, Wolf-in-Exile.
Jihad: Diamond Shark, Ghost Bear, Hell's Horses, Jade Falcon, Nova Cat, Snow Raven, Wolf, Wolf-in-Exile.
Republic: Diamond Shark/Sea Fox, Hell's Hoses, Jade Falcon, Nova Cat, Rasalhague Dominion, Raven Alliance, Wolf, Wolf-in-Exile.
Dark Age: Sea Fox, Hell's Hoses, Jade Falcon, Nova Cat, Rasalhague Dominion, Raven Alliance, Wolf, Wolf-in-Exile.
ilClan: Alyina Mercantile League, Clan Protectorate, Hell's Horses, Jade Falcon, Rasalhague Dominion, Raven Alliance, Sea Fox, ilClan Star League factions (Jade Falcon, Smoke Jaguar, Wolf, Wolf Empire).
Clan Invasion 3050 - 3061
Civil War 3062 - 3067
Jihad 3068 - 3080
Early Republic 3081 - 3100
ilClan 3151 - 9999