WOOHOO! Its Been A Long Time

That Saikyo Line 205 srs is a limited edition sold at the Railway Museum in Omiya, Saitama City, about 30km NW of downtown Tokyo (on the Saikyo Line), and released 14th October 2007 at the same time that the museum opened. I guess a lot of them were sold there, judging from the number on auction sites, but yours is the original box. It looked like this later:



Edit: removed implication that it is still on sale now!