Highly interesting story, Rob,
about a car being most interesing too.
Go get this data card ... it will contain invaluable info...,
e.g. perhaps already the 129.980 engine number or another code number (like 998) on it indicating some "special order" details.
Enclosed another picture of Stirling Moss ...
picking up "his" 230 SL" together with his then wife Elaine in Stuttgart about 1966 or so.
Alfred Neubauer, aged 75 on that pic, was his former race director at Mercedes and he flagged them away.
This is what the text says:
"
Former racing driver Stirling Moss, 36, being "flagged away" by his old chief, Alfred Neubauer, 75, when he visited Stuttgart, Germany, to pick up his new Mercedes-Benz 230 SL sports car. In the passenger seat is Stirling Moss's wife Elaine"
What you can see is that Stirling's car is a RHD without outer rearview mirror and with black steering wheel...
... basically the same setup as on the colo(u)red Getty picture with Rob Walker mentioned above and also with the M7 registration plate.
In contrast the "M7"-registered car on your Johnson Wax add is a LHD with ivory-colored steering wheel, US-sealed beam headlights and _with_ mirror.
So, clearly a different car.
I would guess only one of both is the "real M7" ..., the RHD,
and that is supposingly/hopefully yours (or your wife's).
Please, can you confirm this?
We need pictures of your car and the engine number and more details and the data card and more details.
Try to find the original documentation of your father-in-law...
What a great story ....!
Congratulations on your great find !
Best,
Achim
and