Hi,
I have a 1960 C15 distributor model. I have removed the outer gearbox cover and replaced the clutch actuating arm - had to make most of the bits myself. Thankfully all silky smooth now and not the dog rough operation it was before.
That's an aside really. There is a bolt 3/16 diamerter x about 2/14 long directly inline with the base of the distributor, adjacent to another case securing one, almost in the centre at the top. It doesn't hold the outer cover on so is it some sort of gallery plug? Can't seem to find any info on it or its purpose. Is it BA or BSC as well please?