The oldest one I have is from 3/3/2000 and it works fine, but I used TTS-1 only. It's still included thankfully.
I just loaded up TTS-1, dragged the .wrk file in to Sonar, and it worked.
Come to think of it, I think these files are older than that, but I copied them from a damaged HDD somehow and the dates changed. I think they are much older than that in reality.