Dieter, I don't think any physical data cards delivered with our cars were date stamped. Mine were not. The data card for my car supplied by the Classic Center includes a date stamp of February 24, 1969, which is incorrect as I actually took delivery of my car at the factory on February 12. 1969. According to the table in our Technical manual, my car was manufactured in January, 1969, which would appear to be right considering the delivery date.
According to Technical Manual data your car and Michael's car were also produced in the month of January, 1969. I do not know of any other production data that we have access to that would provide more specific information. Without such data I don't think it is possible to determine if these two cars were built on the same or successive days or in the same week.
Alex, excuse the highjacking of your thread. In my opinion you will not be able to verify the claim of first 380SL delivered to the US. I agree that the important things are as indicated in posts #3 and #4 above