Engineers of the 354th Fighter Group fit a Packard Merlin engine into a P-51 Mustang. Printed caption on reverse: 'PNA, OWIL 21145 AIRMADA OF LIBERATION Mechanics tear down and tune up motors and parts of one of the fast P-51 Mustang fighters on the Ninth US Air Force in England. The fighting Ninth is pounding enemy-held railway centers, airfields, shipping and military objectives on the Continent in preparation for spearheading the liberation of Nazi-held Europe. KX, Serviced by London OWI to list B.' Handwritten caption on reverse: 'Changing packard Merlin Engine in a Boxted Factory, men of 354 FG 9th Air Force.'