This fake is the commonly seen 'gashed shield' type which pops up repeatedly on ebay. In this case, the coin is lit so that you can see all the pimples on the obverse, as well as the uneven surface. Note the blobby stars and the rounded top of the 1 in the date. Unfortunately, 24 bids and over $240. http://cgi.ebay.com/1846-O-SEATED-L...286.c0.m14&_trkparms=66:2|65:10|39:1|240:1309
It's a very obvious fake if you know what to look for but I'm sure it looks genuine to those that don't. That's gonna be an expensive lesson for the unlucky person who wins this auction.
That's not the same gashed shield that I'm familiar with. The one I know has the gash through the horizontal stripes above the banner. Also used on several different dates/mints. I haven't seen a lot of them recently though, the damaged hub used to create the gashed shield dies was probably retired a couple years ago.