My guess about the seemingly extraneous #54027 is that the auction house was using a boilerplate and that number wasn't deleted from an old description when the new material was added.

The barrel serial number is very small and located 'between the ears' at the latch. Raise and hold the latch, clean between the ears with a Q-tip in order to view the number. A magnifying glass may help.

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Mike Maher #283