Triumph pre unit rigid MK1 sprung hub bearing cover plate, This is correct for 1947 thru 1949 only, Note the bearing came loose and not in a enclosed race as the MK 2 sprung hubs, The race on MK 1 hubs was pressed into this plate, you can see the race in the pics,  and this plate does not have the circular ring ridges on the outer side. In exceptional survivor  condition, usually the lifting flange is cracked and chipped off.