Green Bay PackersHe is of course referring to this logo, the beautiful interlocking "GB" worn on caps from Vince Lombardi through the 1970s.
A little explanation:
This interlocking G & B, set in chamfered type, is a nod to one of the early Green Bay Packers logos.
Dad Braisher's "G" helmet logo, but but as a "what if?" exercise I like McInerney's design a lot more than I do some of the others which have been proposed.