Silver-seeker, when you list those old Tek's, it was a "trip down memory lane".
I'll never forget when ....... in about 1983, a Teknetic's dealer , from a far-away city, came to speak to our club meeting. Now bear in mind that in 1983, TID was still new and revolutionary. So most of us in the room where only familiar with progressive-knob disc. Ie.: if you elected to knock out tabs, then you would automatically miss gold rings and nickels. This was just "taken for granted" as the cost of disc'ing out foil, tabs, etc....
However, picture this: the fellow doing a table demonstration in front of 25 or 30 md'rs. He waves a foil wad. It gives one sound. He waves a nickel. It gives another different distinct sound. Then he waves a gold ring. It gives a 3rd distinct different sound! We were all awe-struck! Several guys in that room rushed out to buy their own Tek's, thinking they were now finally going to get rich digging gold rings till their-arms-fell-off. While effortlessing leaving foil and tabs behind. I mean, it's hard to argue with proof like you'd JUST BEEN SHOWN, right ?
Needless to say, we all quickly got a dose-of-reality, when we learned that there's still a heck of a lot foil globs, tabs, can-slaw, etc.... that reads exactly like gold rings. Doh ! Still though, they were ahead of their time.