badloki

Aquired from non-collector owner via Craigslist Sunnydale, CA Serial #: 25719N Ticket on heavy shielding: 99 08400023 Sticker on RF module shielding: CA010410 273S7744 Switch board markings: Lot #6 6/5/78 and C10462 REV B CPX No date ticket on the main board A B Channel Select slot with no switch inside

I'm new to this forum and i have just started my first Heavy Sixer refurbish. I soaked the case parts for cleaning and there was a rubber ring floating in the water when I was done. It is approx 1/2 inch in diameter, flat on 1 side and rounded on the other. Is this part of the assembly or just random junk. thanks