Unmarked insert. Wheel has non-diagonal ridges, and wheel rivet may be damaged/repaired.
U.S.S. Edwards was a Clemson-class destroyer, DD-265, originally commissioned in 1919. It was transferred to the Royal Navy in 1940 with 49 other destroyers as part of the Destroyers-for-bases deal. "CMF" is likely an officer or crew member before the decomissioning and delivery to the Royal Navy on 8 October, 1940.
Both sides were initially filled with black enamel, though up to one half is now missing.