Here's a link to a page with some Cavalier serial number information. I didn't see serial numbers for the square tops, but there is some interesting Cavalier stuff there if you'd like to take a look anyway. I don't know how accurate it is.
http://www.grandamericajukebox.com/page13.htm Thanks, I've already looked there. I'm sure somebody knows. The information has to be out there somewhere. The key to it is figuring out how to decode the serial number.