A '55 Mercedes Gullwing sold for over $4.5 Million this weekend. This is an interesting article about the beginnings of the Mercedes SL and this particular car.
Rare 1955 Mercedes-Benz 300SL Alloy sells for record $4.62 million

 

The 300 SL isn't really the ancestor of the Crossfire, it's the ancestor of the current SL. Since the Crossfire is essentially a reskinned SLK, it's ancestor would be the 190 SL. The 190 looked a lot like the 300 on the surface, but in all regards it was the baby brother of the 300 - just as the SLK is the baby brother of the SL.

As for that alloy bodied 300 SL bringing over $4 million I actually found the "regular" Gullwing that sold at Barrett-Jackson for $2 million plus to be the more impressive sale. Why? One would expect that an extremely rare alloy bodied example wold bring big bucks (they only made 29 of those, after all), but when the best "regular" Gullwings have recently been bringing $700k to $950k it was astonishing to see one gavel down at more than double that. Other than a reprint in the original color it was all original and complete, and had just over 4,000 miles on the clock.