I truly don't believe CBS cared about the authenticity of the documents. Any idiot can see that the signatures are erroneous, not to mention the different tones in the letters.
When I first saw the documents this morning, they didn't look like anything produced in the '70s or even the '80s to me. But I don't know if that was before or after I heard the forgery allegation. Either way, with 5-8 people looking at these documents, the minimum CBS should have had if they had intended to be objective, at least one or more persons would have realized these things were 3 dollar bills.
Bingo! The article states that some of the CBS people thought the documents were fake, but CBS ran with the story anyway.