[Lynn Eades]

Tony the CMPs that used that system were the Carriers, not for a full flow filter, but for the oil cooler. (as with Aust. carriers) They had a bypass valve that let the oil by pass the cooler if it was too cold and thick. (later in the war the Canadians added a filter to that system in the Carrier, Universal, MkII*
I am sure you would already be aware, but the "partial' system you refer to is/was called a "bypass" system. The bypass system used a finer media in the element. it was supposedly to catch the very fine particles and was intended to stay in service for longer. Only a small percentage of oil from the pump was diverted through the filter. Often removing the lid, you would find them pretty much clogged up. I believe that any filter housing that you removed the lid to get at the filter was a bypass system. The British tended to use throw away steel bodied filters. Around WWII a bypass system was the standard filtration system common to most makes of the day.