Matching numbers are nice but add little to the value of the car. Maybe some day it will mean something but right now they are not brining more at auction.
Dan is right, of course, but it is worth exploring what this "matching numbers" thing really means.
In the world of American cars, there were certain very rare muscle cars of the 1960s and early 70s until the genre went away. Cars like Shelby Cobra Mustang GT350, GT500; Plymouth Super Bird, Hemi 'Cuda,
ad infinitum.
Most of these muscle cars started their life as humble family sedans or coupes until the engineers got hold of them. They made small numbers of the rare ones.
Fast forward to today, and it isn't difficult to take a large engine from another junked car (say, a Ford big block 427); slip it into a Mustang, and tart it up to be something eles. Or convert a GT350 to a 500. Or stick a Chrysler 440 into...you get the idea.
NOW, the numbers don't match. You don't have one of the "rare cars" but a pedestrian sedan that somebody made either trying to be fast and furious, or trying to dupe an unsuspecting buyer, or capitalize on the price differential between pedestrian and rare.
WE don't have that kind of issue here, because there are not (sorry, 250 SL owners...) rare versions of our Pagodas that command a large price differential. I do understand that some sort of rare MB cars have been "fabricated", such as converting a rare coupe (280 SE 3.5?) to an even rarer cabriolet...that pricing differential will make it worth the restorer's money if done right, I would suspect.
However, the nice thing about matching numbers from the data card is it will tell you the pedigree of the car, and how well it was maintained. I personally would not want a 230 SL with anything but a 230 SL engine. It would not matter much if that engine had been rebuilt or changed along the way, as long as it was changed properly.