I agree with Buxvet. There is a certain minimum grade that you want to try to get in older issues. That's a blue seal so its pretty rare..but if it were a black seal it wouldn't be such a hot deal.
I used to think that whenever I got a note below BV it was a great deal. I've since revised that assessment since selling any particular note is not the same as buying. Whenever I tried selling those "bargains" I learned the hard way (exactly what kind of deal I got).
Mind you...at times these cheapies we get from eBay can sometimes be good "traders" at shows and when the price is that good (provided it doesn't have a tear as well as writing on it) than you are up in the long run. You simply cannot trust how most sellers grade their notes unless they're very established reliable collectors/dealers we know through CPMS (ie: Sudzee, Tom, etc) I doubt that's a fine.