I've never seen those
Sunn monitors, but I think I know where they "borrowed" the design...
That's a JBL 4612 Cabaret monitor, it's loaded with two 2118J's and a 2404H "baby cheeks" tweeter. I have a pair of them and they get a lot of use; as mains for small acoustics gigs, high packs with a subwoofer for small-medium venues electric gigs, and as side fills for bigger venues. But they are a lot beefier, rated for 200 watts continuous with the compression driver wide open. The 8" drivers are rated for 200 watts
each, if you attenuate the tweeters the cabs will pound pretty hard.
No help as far as those Sunns go, but I would assume they are sort of the "economy" version of the 4612 appropriate for lower SPL applications.