Correct Idle Speed for 87 560sl

I recently acquired a 87 560 sl with in great condition with only 37,000 miles on it. (My bosses car). The car had checked out fine by a MB mechanic and I've had all of the fluids changed. My question is that this idles at about 550- 600 rpm and tach registers 500 rpm when foot on the brake at a light.
Starts up great, seems to idle smoothly, no hesitation, bucking or stalling problems. Since all of the american cars I've owned in the past ( mostly older vettes) idled at 750, I was wondering if the numbers my mercedes is showing are normal or should I have the car looked at as a precaution. I am planning my first major road trip next weekent ( about 5 hours to cape may NJ) and don't want any unexpected problems.
Any input would be greatly appreciated. Thanks

[Deltacom]

Steve,

Your car idles as it should, in "D" and at operating temp should be 500-600 RPM.

[domchang]

my 87 560SL also idles smoothly and at 500-600rpm....