Hello cointalk, I have found a bill in change that has what seems like a minor double die on a coin, but instead it is in the serial number of the note. It is in the 6 on the right number. The left one is just a picture of the other serial number, which is normal.
The 6 between the 7's in the top serial number is basically darker (more ink) than the rest of the numbers and the numbers in the counterpart (lower pic) serial number. To the best of my knowledge no you don't have anything worthwhile just an interesting conversational piece. The 6 that is darker is actually correct the other "lighter" numbers are the ones that are slightly under-inked. From the pics it looks like the 7 to the right of the 6 and the 3 next to the 7 look a bit darker just not as dark as the 6. However all the numbers are all still highly visible and well struck meaning they don't have any missing parts (8's becoming 3's or the G becoming a C) or even numbers missing from the sequence. Eventually in this printing run the numbers would have eventually started to disappear in part and then as a whole meaning in the end there would only be white paper with no serial number at all provided no more ink was added to the machine's ink wells. Also check to see that no other parts of the note are missing anything front or back, check to make sure none of the numbers are rotated or that there are any ink smears caused by additional ink are visible. If none of these are present then it's spendable in my opinion. As always check with a dealer if you are in doubt or a note just doesn't look right to you just to make sure as pictures can be deceiving compared to the coin or note in hand.
I see nothing that would make this collectible. You say "doubled die", I say more like "machine doubling"...... just a normal processing anomaly.
I don't really see anything from the images. If you find a note and one serial number is darker than the other, this is called over-inking which is very common. Maybe worth a buck and a quarter as I can see that it has definately been circulated.
Seeing as these are produced through a roller system, the possibility of doubling is pretty small. Folding, missing numbers/2nd/3rd printing, off center, are more possible and should be taken into consideration. Currency collecting is quite a bit different than coins when you're talking errors.