Looks like a DIIv. There should be a movable condenser behind the nameplate opening (lift at the red buttons). You move this condenser to change formats. I had one decades ago. My memory is a bit lax, after all that time, but I seem to recall you didn't need different cones. The variable condenser allowed you to work with a flat lensboard. Make sure you get confirmation from others, though. Like I said, it was a long, long time ago... Great enlarger, by the way. Yours looks to be in superb condition.