Alternatively, you can purchase a previously issued 3x3 standard combination as follows: Three letters (provided they begin with N, O or P) followed by three numbers, or three numbers followed by three letters (provided they begin with A, B, C, D, E, F, G, H, I, J, K, L, M, N, O or P). Visit Create A Plate® to check your combination. For example NOT007, 123OVR, PET111.