Suzy,
for the DMV, and insurance, your 280SL should be registered with its full VIN, 113 044 10 016402 if it is a manual, or 113 044 12 016402 if it is an automatic.
The 250 SL would accordingly be 113 043 12 001748.
Using the model designation plus the last 6 digits of the serial number is not correct for registration purposes.
Klaus
1969 280 SL