My oil seals were BMC type, like a small thick O ring, if memory serves correctly. My 1948 4G was usually fitted with a sidecar, often containing a young lad called Rob, and was used for some long journeys, so possibly worked rather harder and got warmer than Cynric's solo bikes.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.