An input test. Notice how it contains a C button, even though no such thing is on actual hardware. Pressing this button in MAME doesn't seem to do anything.
in the header of the rom, a copyright notice regarding the gamekey unit is found.
By using this GAMEKEY expansion pack ("the Unit"), you agree that you 1) may only use the Unit with the specific JAKKS Pacific, Inc. ("JAKKS") TV Games(tm) controller for which it is designed; 2) will not attempt to use it with any other TV Games controller or with any controller not manufactured by JAKKS; 3) in agreeing to the terms herein, have a personal, non-exclusive, non-transferable, limited license to use the UNIT as limited herein; 4) may not sell, sublicense, distribute or rent the Unit or use it with any other non TV GAMES(tm) product or device; 5) will not reverse engineer, decompile or disassemble the Unit or otherwise attempt to derive the source code (except where expressly permitted by law).
This Unit is licensed to you pursuant to the terms herein and is protected by copyright law and international treaties. Any unauthorized reproduction, distribution, rental, digital transmission or other infringing use of this Unit software is strictly prohibited. The FBI investigates allegations of criminal copyright infringement. Title 17, United States Code, Sections 501 and 506). VIOLATORS WILL BE PROSECUTED TO THE MAXIMUM EXTENT POSSIBLE UNDER THE LAW.
Just like with all GameKey cartridges, a test is made to make sure its running on their branded hardware. In this case, it does a check to see if it is running on an NK unit. If the check fails, an error message will appear. This can also sometimes be done by messing with the cartridge on startup.
