Several sites report it as a replica, but I believe it was a wind tunnel test, airframe. It is reported as never having a USAAF contract number.
It may also have been built up from spares, for the NACA tests (again no assigned contract number).
NACA used a full-scale P-38 airframe in the Langley 30 x 60-foot wind tunnel, and they also used a 1/8 scale model to solve flutter tests, that killed several pilots c.1941.
John