OK, this one is becoming a fun challenge..............
I will post here a photo of one of the Boonacker Lincolns which was owned by the same company as the Cadillac in the quiz photo. This is a post-war photo and the Lincoln is a post war model.
The original of Fabrizio's photo showed the registration plate number, L-26251 when that photo was taken and I believe this was before the war looking at the car behind it.
Now, the post war photo shows the Lincoln with that same registration plate, L-26251 and behind that car is what looks to me like our elusive Cadillac and I think the registration plate on that one is now L-26250. As we say here in my country, "How you do dat?". Doesn't seem very legal to me.
Anyway, I am still pursuing the final answer and will post again if I come up with anything more.
Bill