test tone

I said something before about Scientist giving us the test tone "dub beep". I might be wrong. I found a track credited to King Tubby "A Heavy Dub" which I think uses the test tone. Now theres a few things about this which make me uncertain: the famous Tubbys mixer was a self built 8 channel unit and in the pictures I've seen, there is no test tone button, maybe this was done later since the track wasnt dated; the other thing being is that it could have been a Scientist mix while he was working for Tubbys. No date on the track so hard to know. I cant find a reference as to when Scientist started working under his own name so I have no way to check this. If anyone knows please comment.