It can't be as early as '41 because it's got internal trunk hinges. The hinges are external on a '41:
Edit: Or maybe not. I'm finding some with and some without visible hinges. The more I look at photos of these cars, I'm beginning to believe it's impossible to nail down the year precisely based on the single photo we have. There were so many different Buick models and variations back then and they all look pretty much the same for almost the entire decade.
I think the best that can be said with certainty is that it's a Buick from sometime in the 1940s. Figuring there's a good chance it's a new car skeezix's father purchased shortly after discharge in '45, it's likely a mid-decade model.