What's This From?

"This is Hi-Fi... high fidelity. What that means is that it's the highest quality fidelity. It has the TK-421 modification which gives it 4 quads per channel. So basically you get twice the bass with the TK-421."

I know, I know, it's too easy. It still makes me laugh.

Can anyone tell me where another completely unrelated reference of "TK-421" appears?