You said he fake was made in the 20th century. Was the original it intended to mimic also from the 20th century?
If not, XIX?
XVIII?
XVII?
XVI?
XV?
XIV?
Before that?
Is the text handwritten?
Is the text printed?
Does it bear a picture of a person?
Does it bear a picture of a landscape scene?
Does it bear a picture of a small inanimate object?
Does it bear a picture that was photographically captured?
Does it bear a picture that was drawn by a human?
Does it bear a picture that was generated by a computer?
Is the text handwritten?
Is the text printed?
Does it bear a picture of a person?
Does it bear a picture of a landscape scene?
Does it bear a picture of a small inanimate object?
Does it bear a picture that was photographically captured?
Does it bear a picture that was drawn by a human?
Does it bear a picture that was generated by a computer?
Is it related to music?
[del]Does the paper mainly consist of written or printed words?[/del]
nm, Chronos already asked.
Is it some kind of contract? A will?
Was it Chamberlain’s piece of paper?
20th century.
YES
Was it an autographed picture?
The picture was real but the autograph was not?
Was Elvis involved?
kk
Popstar?
Rockstar?
Male?
Female?
Dead?
Michael Jackson?
**Les paid $2000 at an auction for an item even though he knew most of what made it valuable was fake. What is it and why did he pay so much?
**
Is the rockstar the one who was pictured?
Is the purported autograph of the rockstar?
Are pictures of this rockstar rare?
Does the picture date from the timespan the rockstar was performing?
Is the picture of the rockstar performing music?
Is the picture one that could plausibly be the rockstar performing music?
Does the picture show the rockstar doing anything he would have preferred not to be seen doing?
Is the signed name a pseudonym -something like “Ziggy Stardust” but signed by Bowie or “Billy Shears” signed by a Beatle?
NO
Is it a relative of the rock star, something like John Lennon signing for Julian Lennon?
Or a rock star who signed a silly picture of some kind purporting to be another rock star as an attempt at humor?
No. Nice idea, but no. 
YES
I think we can fully solve this and have a great little wrap-up. Anyone want to go a bit further? I think it’s too early to call it solved, the specifics are great.
Were they in the same band?
Were they friends?
Rivals?
Was the humor critically meant? (For example someone making fun of KennyG.)
kk
Beatles?
Nirvana?
The Doors?
The Who?
Beatles. We’ll call this one solved.
John Lennon signed all four of the Beatles names on a picture in a newspaper. He wrote “All the best from the Beatles” at the top and then signed for Paul, Ringo, himself(the only “real” part), and George.
The fact that Lennon did this made it unique and more valuable. Apparently, people think he just did it for a laugh.
I changed a detail. Les was the photographer, not the buyer. He was the one to realize Lennon had signed all four names and consequently, made it more valuable.