Neo Geo Pocket:Model Differences
There are three Neo Geo Pocket models.
Models
"Neo Geo Pocket" (1998-1999)
This is the first version of the NGP, and the only one to not support color. Released only in Japan, this model was swiftly discontinued in favor of the Neo Geo Pocket Color. Appears to have only came in a "matte black/checkered" color. Easily identified by it's screen bezel, which lacks any text on it, except the console name on the bottom. This is in contrast to the Color, which has the word "COLOR" on the top right of the bezel. It is also the slimmest of the 3 systems. Furthermore, a non-color NGP's screen appears completely black when turned off, compared to the Color systems, which appear more green/grey when turned off. Lastly, there is a minor difference with the power button on a B&W compared to a Color system - the button is slightly further away from the top right corner.
"Neo Geo Pocket Color" (1999-2001)
With this version, color is introduced to the Neo Geo Pocket, alongside an American release. These systems came in a variety of vibrant color schemes, and feature the word "COLOR" on the top right of the screen's bezel in an italicized red font. Furthermore, these devices are thicker than the original NGP.
"New Neo Geo Pocket Color" (1999-2001)
A slimmer and redesigned version of the Pocket Color only released in Japan. Can be distinguished by their slimmer and lighter build compared to the original Color, alongside the font on the top right of the bezel, which remains red but is now outlined and in cursive. Some press releases from the era also claim this version has superior sound output to the original color.
K2_VIDEO (???)
The K2_VIDEO is a developer unit that has controller ports and is able to output video to an external monitor.
References
https://en.wikipedia.org/wiki/Neo_Geo_Pocket
http://lovewithoutanger.blogspot.com/2015/06/neo-geo-pocket-comparison-b-color-new.html
https://archive.kontek.net/sngp.classicgaming.gamespy.com/hardware/nngpc/nngpc_specs.htm