Jacques, very interesting. Didn't realize ARC was a double word play for Avions René Couzinet and also allowed for the French word for rainbow.
I have never noted the wing tip differences before. All examples I have seen are like the gold variant.
I would suggest, therefore, that the gold wing is the standard one and the white one was, perhaps, hand finished at the factory to correct some anomaly giving it the rounded shape. Perhaps John or Sir George have a better idea. It does look 'factory original' to me so this could be an explanation.
I have no idea about the underwing differences. The ones I have seen were like the gold version.
In the book we did, all 11 photos of the ARC en Ciel shown have similar wing tips to the gold example.
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Dinky Toy Aircraft, 1934-1979, with John Beugels and Sir George Cox, available and a 20% off coupon. This version has many improvements, corrections, more photos, and updates based on the first edition (many thanks to Jacques du Jardin for his superb knowledge and editing skills) and more photos.
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