As I write this there are 3,653 hits when I search Ebay for "Japanese sword".  I would guess that something like 50 of them, if even that, are the real thing; the rest are modern fantasy pieces, modern reproductions, and out and out fakes.  To make matters even worse for the beginning collector, there are fraudulent listings: stolen descriptions and pictures, hijacked Ebay identities, and more.  Given the high value of real Japanese swords, buying them sight unseen based on a couple paragraphs and a few pictures from someone you don't know is not for the faint of heart.
    Ebay will allow only 10 pictures in a guide so I've used my ebay 'ME' page to present a side by side comparison, complete with lots of pictures, of real and fake Japanese swords.  I also discuss sword scams on ebay, sword care, polishing, and a few other items you might find useful.  If you'd like to see it you can get there by clicking on this link or by searching for seller greyguy0 (that's the # zero, not a capital o) and clicking on the ME button there. Once there, please come back to this page and rate my guide.  With a  higher ranking my guide will be seen by more people and fewer of them will find out the hard way the difference between real and fake Japanese swords.
    Hope you find this helpful; thanks for looking.  Take care,  Grey  (greyguy0)