Generally Glasurit is the original paint manufacturer. They have the best quality clear coat available. Even my local paint supplier - a NAPA store that sells DuPont, says the local guys who do restoration work on show cars all use the Glasurit clear coat. It is the clearest clear available. It is all the body shops around here will use on Mercedes. On your paint tag under the hood the color code should have a G for Glasurit or an H for Herbert Standox.
Standox paint was bought by DuPont. I think Du Pont is the best general paint out there. But Glasurit beats their clear. Volkswagon and Mercedes both use Glasurit.
Here's their website
http://www.glasurit.com/