Can't quite make out the s/n #, but it looks to be either 40-748 or 40-749 from J Baugher's list below.

P-38 of the 1st Pursuit Group during maneuvers in 1941.




40-744/761 Lockheed P-38 Lightning
MSN 222-2215/2232. Model 222-62-02, designated P-38-LO, later RP-38
744 modified at Wright Field for aeromedical experiments with asymmetric
positioning of cockpit in port boom. Scrapped at Bush Field, GA May 7, 1945
745 to CL-26 at San Bernardino, CA Apr 27, 1943
746 to CL-26 at Muroc AAB, CA Jul 27, 1943
747 crashed at Muroc AAB Jul 24, 1942. To CL-26 at Curtiss-Wright Tech Institute, Glendale,
CA Mar 24, 1943.
748 crashed into bay 500 yds offshore of Hamilton Field, CA May 18, 1942. Pilot killed
749 to CL-26 at March Field, CA Jun 15, 1943 750 condemned at McChord AAF, WA Feb 13, 1943
751 to CL-26 at Bolling Field, DC Sep 21, 1943
752 to CL-26 at Santa Maria, CA Apr 30, 1943
753 scrapped at North Island, CA Feb 4, 1945
754 crashed on takeoff at Patterson Field, Oh Aug 19, 1941. Pilot killed
755 crashed on takeoff at North Island, CA Mar 13, 1942. Pilot killed
756 scrapped at Patterson AAF, OH Jun 29, 1945
757 scrapped at San Bernardino, CA Nov 28, 1945
758 surveyed at San Bernardino, CA Aug 1, 1943
759 scrapped at March Field, CA Jul 3, 1946
760 crashed near Onalaska, WA Nov 24, 1942. Pilot killed.
761 to CL-26 at Spokane, WA Mar 7, 1943
40-762 Lockheed XP-38A Lightning
MSN 222-2233. Model 622-620-10. Prototype with pressurized cockpit. Scrapped at Bush Field Mar 28, 1945.
40-763/773 Lockheed P-38 Lightning
MSN 222-2234/2244. Model 222-62-02, designated P-38-LO, later RP-38
763 W/o Nov 5, 1941 at McClellan Field, CA. Condemned Mar 19, 1942
764 wing ruptured in flight Apr 4, 1943 at Ontario, CA and landed OK. To CL-26 Apr 23, 1943
765 scrapped at San Bernardino, CA May 22, 1945
766 crashed during emergency landing attempt at Beaufort, SC Oct 16, 1941. Pilot killed.
767 in midair near Natchitoche, LA Sep 19, 1941. Pilot killed
768 W/o Jul 21, 1942 at Mines Field, CA. to CL-26 at Lockheed Sep 5, 1942
769 scrapped at Hill Field, UT Jul 23, 1945
770 in midair off San Diego, CA Dec 21, 1941. Pilot killed.
771 to CL-26 at March Field Sep 6, 1943
772 scrapped at March Field Feb 2, 1945
773 DBR 15 mi E of Muroc AAB Feb 11, 1942
40-774/809 Lockheed P-38D Lightning
MSN 222-2245/2280. Model 222-672-08, later redesignated RP-38D
775 Wfu at RFC Ontario, CA
776 W/o May 3, 1942 at Muroc, CA
777 W/o Apr 15, 1942 at Muroc, CA
778 Wfu at RFC Ontario, CA
779 W/o Oct 6, 1943 at Mendota, CA
781 W/o Oct 15, 1941 at Richmond, MI
782 W/o May 25, 1942 at Mills Field, CA
783 crashed and burned at Mills Field, CA Jun 15, 1942. Pilot killed, plus crew chief on the ground
785 W/o Dec 10, 1941 at Economy, IN
787 W/o Mar 24, 1942 at Mills Field, CA
788 W/o Nov 13, 1941 at Palm Springs, CA
789 W/o May 12, 1942 at Muroc, CA
790 W/o Mar 7, 1943 at Ontario AAF, CA; repaired (?); wfu at RFC Ontario, CA
791 W/o Aug 2, 1944 at Ontario AAF, CA
792 W/o Oct 7, 1942 at El Segundo Pier, CA
794 W/o Jun 22, 1942 at San Francisco Bay, CA
796 W/o Nov 12, 1942 at Muroc, CA
798 W/o May 27, 1942 at March Field, CA
799 W/o Feb 20, 1942 at Los Alamitos NAS, CA
800 W/o Nov 17, 1941 at Woodruff, SC
801 W/o Mar 29, 1942 at Pt. Vincente, CA
804 W/o Jan 14, 1942 at NAS San Diego, CA
805 W/o Dec 21, 1941 at 10 mi W San Diego, CA
806 W/o Dec 17, 1942 at Paine Field, WA
807 Wfu at RFC Ontario, CA
808 Wfu at RFC Ontario, CA
809 Wfu at RFC Ontario, CA