Hello & sorry for this late reply.
After having checked my 4 Silver models I can confirm that the S/N of this particular model is in at the same place for all S Sonnar ( located on the external ring of the objective). It includes 7 figures and all in the vicinity of 2 5xx xxx.
No external particularity except the colour -with or not the Oak crown-
and also the black presentation box (rare).
Kind rgds from France = JL +