How cool!
http://www.dialbforblog.com/archives/558/
From THE JACK KIRBY COLLECTOR 42 back cover, here's an unused cover to JIMMY OLSEN 147 (March 1972, Kirby's next to last issue).
Kirby pencils/Murphy Anderson inks.
This cover was apparently rejected, and the issue ran with an unusual
Adams/Anderson cover.
For a Kirby run of only 15 issues, I've seen at least 4 unused covers, many unearthed in publications like this, or reprint editions.
Volume 1 and 2 of the JIMMY OLSEN reprint trade both present previously unused Kirby covers on them. While Anderson is always nice, I'm amazed how Anderson even dominates and eclipses pencils as distinctive as Kirby's!