Perhaps I was mistaken about the filter, as I looked a bit more. I was thinking of the German G28T, based on the Model A and B engines. I assumed filter when reading about the full pressure.
Probably no filter on that engine.
This could be a reworked anything, as I did a bit of research and there are some outfits that rework these engines to have a full pressure system, including an oil filter.
The G28T was full pressure, but I don't think it had an oil filter. At least not in its original form.