Original US Army, WW2 era, shoulder sleeve insignia (SSI). The patch would have been worn on the shirts and jackets of US GIs who served in this unit.
This particular variant is stitched in cotton, on felt. This type of British made insignia was made by local tailors and available for 'private purchase' to the Airmen based in the UK. The black backing is very typical of British made patches.
Slight discolouration on the front, more on the rear, possibly removed from a scrap book.