Most of the classes look the same, but can anyone help me decipher the award/upgrade classes?

These I understand --
F, C, D, Z, Y, B, E, M, U, H, Q, V, W, T, S, K, L

These I am not sure of --
YN, HN, G, N, XN, X, FN, FE, ZN, ZE, R, O, I