Almost every week i am asked to give an opinion on a Muhammad Ali signed item that is also signed aka Cassius Clay. These signed images are most common in the larger sizes and were sold i believe in the hundreds by various sellers here in the UK in the early 2000's. In some cases they were multi signed and sold as "Champions Forever" with various other boxing signatures, all of which were fake. The same image keeps cropping up time and time again and if buyers were only to do some basic research they would find that these items were signed not by Muhammad Ali but by John Olsen in the USA. Most of the ones i see here in the UK have a COA from a Gallery in Bournmouth, which is now long gone, but you can see them crop up on ebay on a regular basis!
John Olsen was the master forger behind these items and they were sold via dozens of dealers in the USA and to various people here in the UK. Kevin Nelson the author of the book "Operation Bullpen" and the FBI estimated that he created at least 10,000 of these items during his forging career, and ended up in jail as a result. It is rumoured that he is now out and has been doing the same thing again though!
So if you are considering buying any Ali signed item then you need to take a good look at the "Olsen Ali" signature shown here as his (John Olsens) style did not change a great deal during the time he was doing these. There is much more on John Olsen and 'Operation Bullpen' to be found on this site and on the internet.