This is the starter end housing for a post war Rolls Royce. The large flange is approx 4" across, the small cover 2 1/4 diameter. There is a pawl mounted in a bearing. It spins freely but the bearing may need to be replaced.
According to a reliable RR source this should be for a 1946-1958 6 cylinder RR with a manual transmission.
Sold as is.