DB13W3 

Jon Obst attempts to hook up a most unusual Apple Macintosh Portrait Display monitor to his Macintosh II si. But it’s not easy. The display uses a most unusual DB13W3 to Apple DB-15 connection. Not only that, but the display uses a non-standard 640 x 870 fixed resolution at 75hz.

More info on the cable itself (which you’ll likely need to make yourself), can be found here.