In all my years of reading and collecting comics, I've come across literally hundreds of contests and promotional sweepstakes offered by comic book advertisers. My interest in each contest would vary depending on how cool the prizes were...some of which definitely did look cool, while most didn't seem worth the hassle.
"First Prize...a Gemini Spacecraft! No put-on. This is for real--the wildest, way out prize ever awarded in any contest: a 19-foot prototype of the famed NASA spacecraft."
"Your Gemini capsule is just like the original. There's a detachable hatch, equipment section, and retro-fire package. Accurate from the ground up!"
"When you win Gemini you'll be at the airport when it arrives in a 'Flying Guppy' Aero Spacelines plane. Your name and picture will be in newspapers and magazines all over the country. How will it feel to present your spacecraft to your city for a park or museum? Famous, that's how."
"There's more. As the grand prize winner, you'll receive a professional Vox 'Serenader' guitar--plus, every Revell Model Kit! Sounds great."