Louis J. Castelli, Jr. was a Chicago stamp dealer. He is known as the dealer who sent Position 75 of the Inverted Jenny to the Weills of New Orleans, to see if they would be interested in buying it. The Weills recognized the stamp as one stolen from the McCoy block. They were forced to return it to Castelli, since the F.B.I. refused to pursue, believing its value to be below their threshold for pursuing.

The full story of the McCoy block was the subject of a September 2014 article by Ken Lawrence, in The American Philatelist