Hope someone can help. I have an older 500 20Ga. and I have searched the gun from end to end and have not been able to find a serial number. It is the old one with the single bar on the tube and Mossberg has sent me the wrong one although I told them exactly what I wanted. They wanted the serial # in the beginning but said it was not necessary. It is not as if this serial # has been removed for it has an original finish on it. Can anyone tell me where it might be located. Any help will be appreciated. Thanks! Bob