It can usually be fixed if you carefully grind out the carbon tracks with a Dremel tool, then fill with epoxy if you want to or need to for strength.
Then to keep it from happening again, you need to get the B+ off that wafer. The plate of RF tube can be fed through an RF choke back to B+, coupled with a cap to the switch, and the bottom end of the RF interstage coil primary lifted from B+ and connected through a .01 or so cap to ground.
Done many of them, no fun but can be done easier than finding a good switch. Probably many of these were junked in the past when the switch burned up and no replacements available when the sets were not all that old.
http://personalpages.tds.net/~pdieten/silvertone4587.html
Not sure who made this one, but Colonial was a big supplier to Sears during this period.