Letipapa, you 'blocked' my reply while I was sending it!
Since I provided this nice shot I can give the following details:
Photo is an original Chance Vought press release of 5 April 1945.
Text attached reads:
'More firepower to Blast the Japs: a Chance Vought F4U-1C Corsair, of the type so successfully from carrier and shore bases by U.S. Navy and Marine Corps fliers, is shown here with four 20 mm cannon, two in each wing. A number of cannon-firing Corsairs are in combat, while others continue to move from Chance Vought assembly lines equippped with the conventional six .50 caliber machine guns.'
