The M-B system will not give engine # based on VIN for
early cars--- later cars, yes. 79 or 80 seems to be the break.

The eng # on Sl's is a real joy to find.

Behind the left(driver side) valve cover, stamped into the top of the engine block.
Put a cover on the fender, take off your belt, stick your head way up toward the hood/windshield union, and peer down, then get out, grab a flashlight,
and do it again. You will find it covered in sludge.
Then get some brake cleaner/degreaser/solvent of your choice, squirt some in your eyes and some on the suspect area.
A rag on the end of a long, skinny screwdriver is sometimes of help.

any US model 75 450 SL should be 117 985 12 xxx xxx.
450 SEL's were 117 986 12 xxx xxx

Why do I remember this stuff? I'm not that old!!

Alternative--
Green and tan sticker stuck to the rear of the fuel tank,
behind the felt/cloth cover/trim panel. Accessible through the trunk.

{On early sedans(116/123) this is often stuck to the bottom of the rear seat.}

The factory glued the "build tag" there on the SL's.
All the same info as on the warranty card--
Paint and interior codes,
Engine/trans and serial numbers.

Happy hunting,

__________________
Todd Haven
Parts Manager
MPH Automotive
Houston,TX