At the time, the team used one size letters with a space for the Gaelic prefix. The Packers haven't had a "Mc" on the roster since Mike McKenzie left in 2004, but at that time they used a small-cap "c" without a space to set it off. It's hard to find documentation, given McKenzie's singular hairstyle, but you can just about see it here:
Perhaps McCoy's space, like the distinctive number "5"s in use then, was standard from the uniform supplier of the day. There was a time when teams adapted their number styles to fit the manufacturers' catalogue, rather than the other way around.