Hmm, I was thinking you were talking about the Coleco Telstar 2600 clone. That's just a straight up pong clone---so....very little? A fiver? 10 maybe? I'd say that you'd be lucky to find a buyer. Maybe you could get lucky and find someone with nostalgia for this particular unit. Compared to most people on this site, I buy pretty much anything----but I don't touch Pongs with a 10 foot pole.
Its probably not worth much but very cool that its coleco branded if you just want to have it in your collection. Seems everything they made back then was gold.