AFAIK, Sunn never made a dedicated bass 4x12, so I think your friend is wrong. Next, what do you mean by "silver rim"? Are you referring to the aluminum dust cap? If so, again, not dedicated bass speakers. In fact, not particularly good bass speakers, even though Sunn did say they'd do the job.
We could help a lot more, though if you could provide some pictures. Front and back, grill on and off would be best.