"A signature's like a fingerprint -- no two people in the world have the same handwriting," he said. "No forger can copy handwriting perfectly."
"If you have somebody that's really good with autographs that understands handwriting they can spot even the best forgery," Keurajian noted. "I've seen thousands of Ty Cobb autographs, so with a Cobb signature you can just put it in front of me and bang, in a second, I know whether it's either real or not."
When it comes to well-known legends like Cobb and Ruth, Keurajian said, "Nine out of every 10 signatures you see for sale of those guys are fake."
"The demand for these autographs is just huge," he explained. "There's literally 100s of thousands of people collecting these types of autographs who are willing to spend big money on it."
The chances of an autograph being a forgery increases with the hall of famers most people have never even heard of before.
"When it comes to the really rare names like the (Christy) Mathewsons, the Willie Keelers, closer to 99 percent are fake," Keurajian said.
Mathewson was a pitcher from 1900 to 1916 and part of the first class of players inducted into the Hall of Fame in 1936. Keeler, an outfielder from 1892-1910, was elected to the Hall of Fame in 1939.
But the biggest problem in vintage autograph collecting is the so-called authentication companies who supposedly examine signatures and issue certificates of authenticity for forgeries.
"Even if it comes with a certificate of authenticity chances are they're still fake," Keurajian said. "There are no good authentication companies in the market today that know what they're doing. Certificates of authenticity carry about as much weight as the Hitler-Chamberlain peace accord of 1938."
He's seen big items sell for between $50,000 and $150,000 which "are nothing but high quality forgeries that have been wrongly certified."
It's the people who don't know much, but want to invest in vintage autographs that are getting "burned" by these so-called authentication companies, Keurajian said.
"A lot of big money's being paid for forgeries by unsuspecting collectors," he explained. "It's really become a problem."
Keurajian urged current and potential collectors to visit www.autographalert.com to "see all the mistakes these companies are making."