What the hell? Haha, that's crazy. Do you know what they used. I only saw Oldboy for the first time recently and it's become one of my favorite movies; This scene being a huge part in that. You just don't see movies filmed this way anymore. I actually can't ever remember seeing a fight scene that didn't cut away. Also, the western soundtrack is amazing.
Here is the cover of the limited edition tin case. recognize it? such a badass scene
I think a white plastic prop was used for when they could shoot it but then CGI was used.
I am curious about how the US version will be but....it will not touch the original.