I am always excited to get the chance to see unpublished artwork from my favorite comics. The first two of these unpublished covers were printed in a Canadian comic magazine back in the late 80's (I think, I can't find the actual magazine).
The first one, issue 15, was scheduled to be released back in 1981, but the series was canceled before its release. It did finally receive a special limited collectors edition in 2004.
The next cover is the never produced second Summer Special. I was told by Richard Comely that only the cover was ever made, none of the interior artwork was ever done.
The third cover is for the unreleased issue 4 of the Captain Canuck Reborn series from 1993. I got this cover from the solicitation in the Diamond Previews catalog back in 1993. I have always been curious if this issue was actually completed, or if just the cover was produced?