* Seikosha GP500M-2 - Was offered as '''Amstrad DMP1''' for CPC (centronics 36pin port) (plus 2K SRAM) (BIOS: 8DE-1)
* Seikosha GP500VC - Was offered as '''Commodore MPS-801''' for VIC20 and C64 (commodore 6pin serial port) ([[Media:Commodore MPS801 Printer Manual.txt|manual]]) (90-byte buffer, no 2K SRAM)
* Seikosha GP500AT-1 - Was offered as '''Atari 1029''' for Atari XL (dual 13pin port) ([[:File:Atari1029 Printer.jpg|printer photo]], [[:File:Atari1029 PCB.jpg|pcb photo]]) (no 2K SRAM) (BIOS: 8AT-1)
The main difference is that the PCBs are customized - the VC and AT models have non-centronics connectors. The ROMs might be also customized, possibly containing different character sets (?), and most probably different protocols (for the serial-port VC version at least).