Technos Japan’s prototype for Double Dragon II: The Revenge, developed and published by Technos Japan, is one of the more unique ones seen. It comes inside a Disk System RAM adaptor.
Some things to note: The “HVC-TK22EPROM-01” on inner board matches outer label; there are TECHNOS JAPAN labeled program & character EPROMS; The title screen shows “Sample Version / 1989 Technos Japan Corp.”; You get UNLIMITED CONTINUES with this prototype; Between continues there is the option to change difficulty settings (and switch between the 1- and 2-players modes); The screen after the start screen says “Double Dragon” without the “II”; The ceiling spikes don’t injure you when you jump into them; You can do jumping knee rams under spikes and your life meter won’t go down.
More differences: The helicopter doesn’t shoot at you on “Easy”; The fortress tank doesn’t vent steam at you; Antagonists become progressively tougher; There are no disappearing platforms or falling fire on “Easy,” likewise with “Medium”; “Difficult” has fast disappearing platforms; The wheels move faster on “Difficult than “Medium”; No spikes fly up in the wheel room on “Easy.”