This is actually a Hong Kong model. I bought an identical unit on Ebay recently, also being classified as Japanese by the seller, so I thought it was a Japanese model. Its a HK unit, but has the NTSC-J region coding. A true Japanese Dreamcast has a sticker that looks like this.
http://imageshack.us/f/804/kgrhqzo4e9cepfmkbpp7fiv.jpg/
I thought my "Japanese" unit was strange when the bottom sticker had only English, no Japanese at all.