I'm not sure at all about these Walkers. I thought that if the breast feathers were not present then it was wear. Then I ended up with a couple of PCGS MS63 1944P Walkers....and they were just as flat as this one. Did some research and found out that strike is a major problem with this series and so leave it to the experts.
But, for what it's worth, I'm not seeing any change in the surface patina that would indicate wear. Also it does seem to have a nice thumb, which I am told is a rarity.
I'll stick my neck out and say MS63, and admit that I could be barking up the wrong tree.