System.ValueType was in .NET 1.0? Interesting, I didn't know that. (There are no docs on MSDN for 1.0, and I came in at .NET 2.0, so that's before me.)
In MDSN, you use the drop-down to change the version of framework you're looking at for documentation. Here is the ValueType class documentation for .NET 1.1:
Believe me, I spend plenty of time up in there to make sure this library I wrote will be cool with .NET 3.5 or whatever. =) I wasn't sure if that had been wedged in with .NET 1.1. I've never seen even 1.1 in the wild.
Thanks!