A few years ago, IBM replaces VisualAge for Java with WebSphere Studio Application Developer, or the WSAD. It was branded at version 4, right off the bat. Just for the record, WSAD is based on the eclipse platform.
WSAD 4 was then replaced with WSAD 5. After WSAD 5 came out, IBM bought Rational Software, and their development tools were rebranded under the Rational name, so the next release of WSAD 5 became IBM's Rational Application Developer, and it was versioned at 6 right off the bat. Again, IRAD 6 looks alot like WSAD 5, and WSAD 5 is very similar to WSAD 4, all of which are based on eclipse.
So, I don't actually think there was a WSAD 6, although some people may use that name to refer to IRAD6.