Difference between 12 ga receiver stamps 500 and 500a

[warren5421]

I am looking at buying a 12 ga Mossberg stamped 500 on the receiver. My Mossberg is stamped 500a on the receiver. What is the difference? I have not physically see the 500 stamped gun just 2 pictures. It has a 20" barrel with a 7 round mag tube. My gun has a 28" vent robbed accu choke barrel. Can't find any info telling me the difference if any. Please help me finding the difference if any!

 

[old mossy]

The 500A is a 12ga.The 500 (assuming) it's a 12ga is the same gun.

 

[Bobster]

500 plain is likely 12ga. Then the letter goes up as the gauge gets smaller: 500A=12ga, 500B=16ga, 500C=20ga, 500D=28ga, 500E=.410"