I've had Taxan, Roland, NEC and Hitachi monitors that used these connectors for RGB. The Taxan and Roland monitors were switchable between analog and TTL RGB - "Apple" mode was analog, IBM mode was TTL. I used the Roland and Taxan monitors on my Amiga. The NEC monitor was TTL only.
It is an 8 pin EIAJ jack. When I was making cables for these monitors I'd cut an old stock VTR cable in half to make 2 monitor cables. Sorry, I don't remember the pinout.
This link here has a pinout for a taxan monitor:
http://wouter.bbcmicro.net/hardware/monitors/index.html