I guess the unsharpened ones are not meant to be sharpened, and the quality of the metal is different. So if u sharpen it maybe the metal will spoil (rust and so on) esp those that u buy from batu ferringhi.. if i m not mistaken its solely for deco purpose only..

and like ijatz said the real katana is made from 2 kinds of metal, they mix it, so the "jisim" from one of metal can fill in into the "jisim" of another metal thus making it super sharp and much more stronger. I read this from somewhere long time ago..

katanas made before the world war are mostly hand-crafted, whereas those made during the war and post-worldwar are machine made cause its faster and cheaper to produce to equip the military. so that's y the pre-war swords are higher in value as compared to the the post-war swords.

another interesting thing about samurai swords are the cut test. in true iaido practise, those samurais/iaidoka will perform cut test on bamboos stacked together(normally). and from what i read, in the samurai days, they actually perform cut test on actual people (enemies etc..)

sorry for the long post, correct me if i m wrong cheers~

Its along Penang Road, at the Campbell street junction (traffic light).
The last time i went there (years ago) i saw a few fancily designed katana, one with a dragon head on the end. And from what I saw it looks almost the same as the ones sold in the US. Perhaps they got the same stock. Its kinda pricey too.

It should be of better quality than those sold in pasar malams, i guess.