SHOTGUN: MOSSBERG MODEL 500A SHOTGUN, SERIAL NUMBER P979153, 2- TONE, CASE NOT INCLUDED, PUMP, 12 GAUGE, 17 Notes: Mossberg 500A 12GA Shotgun Description: Type: 12-gauge pump-action shotgun. Manufacturer: O.F. Mossberg & Sons. Model: 500A. Design: Traditional pump-action shotgun configuration with a practical sporting design. Configuration: 12-gauge shotgun associated with hunting and sporting applications. Summary: The Mossberg 500A 12GA is a pump-action shotgun manufactured by O.F. Mossberg & Sons, featuring a traditional sporting configuration and a durable, practical design.