I saw a reference to this in a closed thread and opened this one to clear up the question.
Konami developed a number of its early computer games for the Amiga, and the screens from several of these (Contra, Rush'n Attack and possibly Ajax come to mind) graced the boxes of other versions. This has led many to assume that the games were released for the Amiga.
I talked to Konami about this back in the mid '90s when doing a story about unreleased Amiga games for Compute!, but don't recall getting a solid answer. There are all kinds of possibilities. My best guess is that the Amiga was simply the development system--not a target system. (Konami wasn't all that high on the Amiga as a games machine in the mid-to-late '80s.)
Hope that's helpful!