Very Nice....at one time that was someone's prized possession.
I'd do a little research on line and see if there is an association affiliation...show it there.
You may be surprised by the responses.
They probably flew a variant of the B25 Mitchell low altitude attack bomber as it has a 75mm. nose cannon for strafing missions (shipping mostly).
http://www.bing.com/images/search?q=b+25+75+mm+nose+gun&qpvt=b+25+75+mm+nose+gun&qpvt=b+25+75+mm+nose+gun&FORM=IGRE