You know the N-number, so if you can find the S/N, you can order the aircraft records on CD here:
http://aircraft.faa.gov/e.gov/nd/This costs $. (used to be $10/aircraft)
I checked Aerofiles on N25577 but the registration database there doesn't have it listed.
If you are positive that the Porterfield in the photo is N25577, (I can't be certain the third number is a "5"), Tom Porterfield posted he thought the S/N would be 677. I've tried several S/N's in that field on the FAA records ordering page, to no avail.
The FAA records that have not been digitized must be physically retrieved. Once they are retrieved, they are digitized and the paper copies are destroyed.
It doesn't matter to the FAA if the paper copies have famous signatures on them, the paper is destroyed!
It is possible that no one has ever requested the records for N25577 using the modern system in place. The correct S/N must be known and used to order the records.
The records on the CD are the registration and airworthiness records. From these you will have the chain of ownership. These records are simply whatever paperwork was ever submitted to the FAA during the course of an aircraft's history.
Let us know what you find out.
Good Luck!