The 10 may be a plant or manufacturer code. If the part number is
120 888 01 15
the 120 would identify a W120, which was the model 180 and 180D built 1955 to 1962. Of course, possibly the grille could also be applicable to other models of the same period, e.g., a model 220; MBUSA Classic Center, Paul Heule or Tom Hanson should be able to tell you the exact applicability.
Klaus
1969 280 SL