Mk 3's on here seem to go for anythign from £65 (rebuilt and a bit battered) to £125 ( very good bluing and stock), condition is important though the early fluted stocked versions are rarer. Judging by the serial number yours should be a series II made between 1949 and 1957. It should have no scope rail if this is correct. If you put up a photo it would be easier to give an idea.