[fsbofk]

Air Group 84 aircraft aboard Bunker Hill in early 1945 displayed a yellow ring around the front of the engine cowl as a temporary marking. Some references interpret this to be a white ring, which may explain the boxtop illustration you mention (in the old Profile for the F4U-1 Corsair, the 5-view rendering showed a white ring - I still have a model of a Corsair I built in the 60s, with a white ring based on that Profile !).