Personally I just go by ERA, and keep dollar tree mini business card organizers per ERA, then if I play in a time period, i just grab the appropriate organizer + and intriguing units from the past eras that will fit, and whala happy and time appropriate games and currently I have a SL,SW,CI,CW,JH,DA folder and it seems to work for me (each one has 5 splits that work great for support (anything nonmench), Light,Medium,Heavy,Assault