This is a weird one. I'd have to go back and see how they promoted the story, but the image may just be of a generic Judge rather than Dredd, per se. Note that the badge he's wearing just says "Judge' and not "Dredd" as well. Also, in the story context, it could be argued that the Judge on the Motorcycle on the first page isn't Dredd, but Judge Alvin, whom "Whitey" the bad guy, kills. Judge Alvin was riding a Motorcycle when he was shot. If the Judge on the Cycle image was not promoted as the Judge Dredd feature, but just a generic story character, then the image of Dredd standing next to the Grand Judge is the official, bona fide first Judge Dredd appearance ever published. In any case, it's a hell of a thing to see up for auction.