No gus, that's the '54. I think they were all round until '54. Don't know if they ever had a cork in them but it bugged me so I made a mold up to cast one for mine and a couple for the shelf. Seems that you could get water splashed up inside traveling thru a heavy down pour.
I think the holes were for draining the tool box if you got water in it, like if you hosed out the interior. After all, they were just work trucks.
DG