Looks like something, probably a sheet of paper blocked the full printing process.
Surprised this bill survived so long for you to find.
The ten dollar bill has gone though a couple design changes from when this was printed.
Is the back a complete print?

Because its not uncirculated, image shows folds, it may not bring as much.
A regular coin dealer may not offer as much because error note collectors aren't plentiful.
I believe the largest paper money show is in Memphis, held once a year.
The Banknote Reporter, monthly newspaper could give you more info on where to find pricing or selling info.

Try this site http://www.coinsite.com/html/USCurrencyErrors.asp