Graham,
The shield on the forward 4-in gun was pretty much a wartime standard mod for all USN destroyers operating as convoy escorts. I suspect the shield was added due to the weather conditions encountered on cross-Atlantic convoy escort duties as gun crew protection and observed RN practice.
So your subject is USS WINSLOW (DD-53), maybe this image will be useful. I came across this image, a postcard, at a vendors table at a Military Collector's Show. A poorer quality version of this image had been miss identified years ago as another USN destroyer, "likely" USS DOWNES (DD-45) ...
http://www.navsource.org/archives/12/1217132626.jpg ... and ...
https://www.history.navy.mil/content/hi ... 92952.html ...) based on the camouflage pattern worn. But, it turns out that USS WINSLOW also wore this nearly the same pattern. You can clearly make out the hull number (on the hull below the bridge).
For completeness, here is an image of USS DOWNES (DD-45) with close to the same pattern.