Coincrawlin,
This is most likely a "filled die" error caused by the die becoming clogged with grease. As to what it's worth, who knows... I save them and have about 6 or so. I only keep them if they are brand new uncirculated. Normally the other side will be normal, but sometimes both sides get filled or you could have a very weak strike (would affect both sides as well). Some are called die adjustment strikes from when they are adjusting the pressure on the machines -- would also be very weak on both sides -- these are suppossed to be quite valuable. My guess is yours is a filled die though. I have sold two nice examples on Feebay over the years. One went for $30 (SWEET!) the other for about 3 bucks. Either way not bad for fifty cents and they are interesting...