All early A-series engines had these rear of the engine side plate gaskets made in cork. For Mini's pre-1966.
The side plate was designed to take the cork type; the later rubber type will not fit owing to the shape of the metal side plate.
The side plate does not have a lip to hold the gasket in place, as per photo.
Recommend: 2x 12A1139 per Mini.
For Mini's 1966 onwards, use 12A1175.