ic-racer is correct; my Dual Dichro S is a black model and appears similar to the unit in the manual he links to, and the manual says that the unit takes a 200w bulb.
I sent my unit, bought inoperative, into Beseler for repair around 2001, and it came back working with the 250w bulb installed. I requested a repair manual from Beseler, also, which consisted of a list of parts and a wiring diagram. If I can dig up the wiring diagram I'll report back on what the diagram says.
I do recall that the heads for the 23CIII are spec'd to fit the III only; whether or not that is true, I have no idea.
Even with the 250w bulb, printing times can be really, really long with this head---about ten times longer than my condensor B22.