Mossberg Expert Need

[warren5421]

I have 2 Mossberg both stamped on the receiver 500a, I am looking at one stamped with 500 on the receiver. Anyone know the difference between the 500 and the 500a? The 2 I have are 28" barrels while the 500 is a 20" barrel. The 500 is the older of the 3.

 

[Itchytriggerfinger]

After a certain year, (1992?) Mossberg started calling the 500 12 ga. the 500A.