Hi, thanks for the warm welcome!
I really admire the 500 series scopes as I think folks have taken pride in every step of designing and manufacturing those instruments, and that's more than impressing. First thing I spotted opening the side panel of my 516 many years ago was a length of solder that obviously has been put there in the factory - just in case someone needs to fix something and does not have the recommended type of solder at hand! Among many other instruments of that era there are quite few manufacturers that could be named as a match in quality. I was able to "rescue" a 585 and a 565 from being scrapped recently as the former owner did just pull out most of the tubes and sold them individually to hi-fi gurus.
Joe
Joe