Vintage Cars: 1955 Mercedes-Benz 300S.L Gullwing, mercedes benz 300s, bonhams goodman

Question
Hello,

I'm producing an ad campaign to promote the leasing of a commercial office building constructed in 1989 in the Washington, DC area. The premise of the ads are based on
“Classics Appreciate in Value.” I need to know approximately what  a 1955 Mercedes-Benz 300S.L Gullwing was valued at in 1989, the same year our building was built, versus
it’s value today.

In 2006 it sold at the  Australian auction house Bonhams & Goodman for $630,000.00 US dollars. Any Ideas about it's value in 1989-1990?

I would greatly appreciate any information you could give me.
Thanks for your time.

Stan

Answer
histrically MB's of this particular vintage have enjoyed  between an 18-20% growth rate.  These are some actual  average price ranges from old sales
$150,000 in 2000, $200,000 in 2001/2002, $300,000 in 2003/2004, $400,000 in 2005/2006, and $550,000 in 2007/2008.
There are many factors in a sale and especially for the gullwing figures above are not representative of "concours" condition cars
You could see another $100,000 on top of these prices and depending on provenance even more.
Hope that helps
Happy Motoring
Ron