The interesting thing about this ad is the four novels fanned out in the corner. Four novels. This is evidence of a book that never was produced. The four Top Secret/S.I. books that we know exist are:
- Double Agent: Acolyte of Darkness/Web of Danger
- Double Agent:The Hollow Earth Affair/The Royal Pain
- Double Agent: The Hard Sell/Glitch!
The fourth book is a bit hard to make out, but I believe the titles are- Double Agent: High Stakes Gamble/Overloads of the Underworld. Yes. Overloads. I'm not sure if this is a typo because this Amazon.com entry is spelled this way.
I wonder if the unproduced Double Agent novel was basically a novelization of the High Stakes Gamble box set. It's too bad it was never released. I would have liked to see more Sebastian Cord.
Also, notice the early box cover art for the High Stakes Gamble box set with the red border.
I do not recall seeing any other Top Secret/S.I. ads in comics those days. But I do recall seeing this ad in quite a few issues.