Anyone notice how the n in New is capitalized? To me that looks like a proper noun, like, I don’t know, New Nintendo 3DS?

Nope. 本体 means the main item itself. 箱 means box, and is getting a B. 説明書 is the manual. The description below is barely readable, but starts with 本体, so I guess it goes on to explain what’s wrong with the Game and Watch inside (how badly scratched it is, etc).