Primary case oil seal

[paul.sammut]

Hi,
I am rebuilding my 1958 Square Four because it had been sitting for a long time. When I purchased it, it had poured oil out of the primary case with ease. I see there is a recess in the inner primary cover, inboard of the large chainwheel, which looks awfully like a site for a large oil seal but my bike did not have one. I cannot find a diagram of the primary chain case nor a reference to this seal in the handbook or on Draganfly's website, but feel fairly sure there should be one. Could anyone please correct me if I'm wrong or provide me with a part number and/or dimensions of the seal?
Thank you in anticipation,
Paul.

[paul.sammut]

I have been reminded that placing a fixed oil seal there is not possible due to the need for the gearbox to move when adjusting the primary chain. Duh, of course. I had wondered whether the rim around the recess wa designed to be an oil catcher, but the recess looked like it was designed to take a seal and that had me fooled. Forgive the question.
Cheers,
Paul.