Look at the Heritage website under currency then the auction archives then errors- inking. You must register if you are not a member but it is free. This is a great site for past prices of hard to find items such as this. I looked for you and back in April of 2006 a lot of ten 1988A notes with insufficient inking sold for $517.50. The notes are very similar to yours. About 1/3 of the note is affected on the back. But their lot of ten (also in consecutive order like yours) all have the inking error. I think you included a good note before and after your run so you really have a run of 6 maybe 7. Still a very good find and I would always keep them together as a set. Congratulations!