You could try to clean it but I'd just leave it alone. As a composite of the two images shown below it is unique and would not deter a boxing PC collector from wanting it. I would have chased it except that I did not want to buy and then have to turn out the other two in the lot.
As for the boxing and other non-baseball fora, I'd prefer they stay separate from memorabilia and autographs. If something has dual potential I list it in both sections.