Inicron's ROM-RAM-Box is a external device connected to the expansion port(with pass-trough), that expands both RAM(by 512kb) and ROM memory.
Technical specs.
Pictures
Software
Inicron delivered the RRB with the Softbrenner Tool. This ROM based software is window driven and allows to manage the RRB. It is even able to convert BASIC or Biary programs to ROMs.