(updated post to correct serial number)
This is a crop (attached) from a very high quality picture of one of the Ingram auction bills
It's the front of L49839325B Series 1963A (in case you want to check against the list of found bills)
It has purple on it, from the silver nitrate used by the FBI for fingerprint checking.
You can see the agent's initials to the left side of the image.
I believe they only did this to bills on the top and bottom of bundles. Not all bills have this purple stain
Why is that important? Well, if there were straps or bundles on the bills, any possible marks might be on these bills.
If you look closely at this image (and no I didn't modify it)...you can see a two thin veritical lines across Hamilton's right eyeball.
Arguable these look like they could have been caused by long term compression/decomposition of a thin rubber band.
I don't think the FBI process would have caused them. They are not on non-purple-stained bills.
Sure it's just speculation, but it's interesting I think.
The speculation is: If Cooper received bills strapped in currency straps, how did this bill get a thin rubber band wrapped around it?