After Burner II/Hidden content
From Sega Retro
There's a screenshot of the DUKE message in an issue of Sega Saturn Magazine (JP) (don't ask which one - I wasn't paying as much attention as I should have been). I'm not sure it can be performed in MAME, so I can't verify that this is a thing. -Black Squirrel (talk) 15:43, 10 January 2020 (EST)