Looks like a slat grille behind the GP.

“1942 Press Photo Jeeps travel across unpaved section of Panama trans-highway.
This is an original press photo. Under the supervision of the U.S. Public Roads Administration fourteen hundred men are at work constructing a trans-ishmanian highway which is scheduled for completion (withal weather paving) by the end of March 1942, if the work is not hampered by rain during the present “dry season”. Photo shows part of the “Jeep” parade over a section of road which has not a yet been laid with concrete. The road is entirely within the Republic of Panama. Photo measures 9 x 7.25 inches. Photo is dated 02-06-1942″

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