The first one is clearly a sheet repair on the underside to fix where the guard cracked through the screw hole. The second appears to most likely be filler to repair probably a deep or unsightly casting flaw; I don't think there was ever a screw in that. The third is RCA42 and it once again is simply repairing and stabilizing an old crack through the guard finial.
Bottom line is these three examples at least all appear to be repairs.