This portrait of what looks like Tomahawk 23 of the American Volunteer Group turned up on the internet a couple years ago. (Related pictures can be seen on the Axis History forum.) I was a believer, but I've since been challenged. "The P-40 in the [photo] is more of a mystery than is stated in the caption," emails Avery Galbraith; "it is not a Tomahawk at all! The considerably different shape of the windows aft of the cockpit canopy framing (I don't know if there is a proper name for them) indicates that this is a P-40D or later, and presumably would not have been in either Burma or China in 1941."
Here's the same plane as seen from the port side. Alas, there appears to be a defect in the photo that would have hidden the numeral 1 if indeed this is AVG P-40 Number 123. (Or perhaps somebody desperately wanted it to be Number 23?)
And here's Number 123, a P-40E ferried from Africa's Gold Coast to Kunming in the spring of 1942 as one of the replacement aircraft obtained by Lauchlin Currie at the White House. I doubt this could be the aircraft shown in the Japanese photos, because the numerals are just too formal.
More recently I've been assured that the P-40 is actually a K model. Here's the email from Terrill Clements who wrote the excellent American Volunteer Group Colours and Markings:
Hi Dan, regarding mystery a/c number 23, close examination of the area where the fin meets the fuselage would indicate that this is a P-40K model. (Note the curved fillet added there to add more area to the fin to improve directional stability, a -K recognition point.) I'm pretty sure that the 23rd FG received some of these in 42-43, and, as far as I can tell, this plane's appearance is generally consistent with those (two-tone camouflage, side number, roughly painted out serial - good photos of the 23rd FG Ks are not hard to come by for comparison.)
But that puts us back in the circle: as far as I know, there was no Number 23 in the 23rd Fighter Group, and Number 123 surely was an E model. Was there ever a 223?
Here's what the invaluable Joseph Baugher says about the K model:
On October 28, 1941, 600 P-40Ks were ordered for Lend-Lease supply to China.... The first P-40K model rolled off the production line in August 1942.... Most of the P-40Ks served with the US forces in Asia and the Pacific and under Lend-Lease with the Chinese Air Force....