Welcome, and nice bike.

It's a 1963 model. They had chrome socks. The serial number indicates when the frame was made. It probably went into a holding pile for a while and was later built up as a 63 model. I have a 1976/1977 Varsity that's like this. Serial number on frame indicates 76 but the head badge and decals are 77.

If your wheel is true and a tire bead will remain seated, I wouldn't give that 1mm difference another thought.