From Sega Retro
The SG-1000 II is an updated version of the SG-1000 video game console, and was released by Sega in 1984. It is not a new system per se - internally it is identical to the original SG-1000, though it sports a number of cosmetic changes and largely replaced the original unit.
Like the original SG-1000, the SG-1000 II runs all SC-3000 games and applications, with the exception of Music and Basic Cartridges. The expansion port has been moved to the front (as it is only used by the SK-1100 add-on), and rather than hard-wiring the first controller, it is detachable like the second. The SG-1000 II also shipped with updated SJ-150 controllers, which can be housed on the sides of the console, a design concept inspired by the Nintendo Famicom. Controllers are plugged in to the back of the unit this time.
The SG-1000 II design would go on to influence the Sega Mark III, which acts as a completely new video game system.
As the system failed to deliver any meaningful improvements for the Japanese public, the SG-1000 II, like its predecessor, faced stiff competition from Nintendo's Famicom and failed to pick up much steam in that region. As far as we know, it was not released in as many regions as the original SG-1000 - most would jump ahead to the Sega Master System.
Aaronix distributed the console in Taiwan starting in 1986, though the legalities surrounding this release are not yet known. Aaronix produced their own software with this console in mind, often converting games from the MSX (potentially without a license to do so). At least three revisions of the console are known to exist, one without the expansion port.